PureExistence1

As salaamun aleikum, few things about istikhara-as someone has already mentioned, istikhara is something that is done when a person is on the fence and can not make up their mind about what they should or shouldnt do. If you have already decided what you would like to do, istikhara is not necessary, rather, make your decision and pray to Allah سُبْحَانَهُ وَ تَعَالَى to make you successful in your endeavor.
Another thing is, and Im not trying to suggest anything bad about the alim you asked, but a persons spiritual purity and sincerity in Islam and in how they conduct their personal life behind closed doors can have a profound effect on how "accurate" the istikhara is. Its advisable to choose someone who has a known good reputation for being pious,just and pure. Even alims have their shortcommings,character defects, and spiritual pollutions that those of us in the community may not be aware of,so best to research into the reputation of the alim as best as possible before you choose one to do it.
Another thing to keep in mind when having one done, is just because something is not "good" right now, doesn't mean it is not good for the rest of Eternity. This universe/realm we live in operates according to a humanly unknowable algorithm. Things are constantly in flux and changing moment to moment,therefore, so will our circumstances and the results of istikhara. Wait a short while, maybe a month or so, let some time pass by, and then have it done again because there is a good probability the outcome will be different based on the algorithm and life circumstances having changed. We never know how things will play out. Maybe if you had stuck with your original plans, something terrible may have come about, but waiting till later date will avoid the bad incident,meaning the istikhara would possibly come back "good" at the later point. We can never know all the particulars that the istikhara takes into account, but Allahسُبْحَانَهُ وَ تَعَالَى does, which brings me to my last point..
There are 7 possible results for the type of istikhara done with tasbeeh-im not talking about the one that involves the Quran as I have no personal  knowledge or experience with those. What I DO know, is Its never advisable to go against the outcome of an istikhara that produces the results of bad/bad in 2 ways/ regret. Why would a person willing go forward with an action that will knowingly bring such results into their life? If you really truly do believe in the istikhara and what it is and how it works, then acting against it once you have an outcome is tantamount to willfully acting against Allahs guidance for your life.. I'd personally rather stay away from doing things like that.  On the other hand, if the result  comes back excellent, good, good with difficulty, or mubah, then you could potentially decide not to do it and just not invite  more good into your life. What you can do in such situations is ask the inverse of your original question. Sometimes a question needs to be asked  a few different ways to get exactly what the best action is. Like for example, should I move to this house in this other City? The answer comes back bad, so you ask the question should I NOT move to this house in this other City? See what that answer is and go from there. Alhamdulilah, istikharas do not cost anything, so you can do many of them to try and get a more well rounded understanding of the results, all you need is someone who has time and is patient to do them with you in the event you have multiple questions.
Here is an example from my own personal life:
It was when my husband and I first temporarily married. He was just about to move to the state that I live in, when things all of a sudden got unexpectedly strange between us. We ended up in a pretty severe argument about some things. I thought it was just a matter of us both being a little upset and stressed out because this was a big change for both of us. At any rate, an istikhara was done for the situation, and the result came back that it was  bad for him to move here, and that it was bad for us to continue that particular  marriage.. I was shocked, because everything seemed to be just great between the both of us, other than this random argument that came out of nowhere the day before he was going to physically move here with all his stuff and pay first last and deposit on our place.. Anyway,I told him the results were bad, and we decided to respect it and not go any further at that point in time and we agreed to end that marriage according to the istikharas results. A few days later, he got a call from Iran saying his father was in critical condition and prognosis was not good, and he needed to go there immediately. He was gone for about 2 months. By going, he was able to reestablish his relationship with his father, visit his aging mom and take care of some other responsibilities that needed to be done.
Looking back in retrospect, it was as if this whole trip back to Iran had to happen first before  starting our lives together, but prior to getting the call and finding out his father was sick, we had no clue why the istikhara came back bad- how would we? These are things only known to Allah, and not the creation. This is the ghayb.
Upon his return, we married again, and everything has been fine ever since. 
 
Another situation I just recently became aware of, involves a young man who just graduated high school and his mom. He was accepted into seven different universities, masha'Allah, but before i go further, i need to provide  a little  back story on his situation-he didn't grow up in a religious family, but they knew enough to know that going to University is a big step in anybody's life, and to seek guidance of Allah in deciding which university he should go to. As many know, a common thing at universities is  drinking, mixing of both genders, drugs, especially when you live the dormitory life. For a young man who doesnt have a strong religious base or upbringing, this is an extremelly dangerous situation for him to go into.It is like going into battle without a sword, shield, helmet, etc. Besides this, each of  these universities are very far from his family, so he would be detached from his support system, all alone in a strange place with many bad influences.
Now back to the situation. Basically what happened, is him and his mom went to visit this very Pious religious and knowledgeable sister. They requested an istikhara for each University that had accepted him, and each istikhara came back bad. The sister who did the istikharas for them started to talk about the possibility of maybe instead of him going straight to University, he should take a year to go to hawza in United States and develop himself a strong religious belief and knowledge base, so that he has something to defend himself with against the evils of the world before being thrust into university life and the world in general. They agreed to do an istikhara for that, and it came back excellent..Would you believe that? 7 istikharas in a row came back bad for each of those universities, but the istikhra for him to go to hawza for a year was excellent. Subhanallah! At this point, no one knows what the end result is going to be, because the sister who did the istikharas for them told me a week later that the woman and her son chose to send him to one of the universities instead of hawza:/  
Dear goodness, may Allah preserve this young man,in sha Allah.  I mean, what are the chances of each istikhara being bad, one after the other, with no variation in them whatsoever? There are 7 different possibilities each one of those istikharas could have come back as, but they each came back as bad...and hawza  came back as excellent...subhanAllah.
 I'm going to wrap this up by saying, don't give up on your marriage and the  situation. Practice patience, and have another istikhara done later, because we don't know the unseen/the ghayb, but Allah DOES, and He only wants whats best for us. I know sometimes what He wants for us may seem like its in direct conflict with what we want or think is best for ourselves, but we have to trust Him. That's part of our trial and spiritual advancement:) Our job is to submit to His will for our lives, and trust Him to guide us right, as He promises in the holy Quran to do so:)
May Allah guide us all, in sha Allah.
As salaamun aleikum