salaam alaykom
advise on not wasting the water and your time.
1: ignore all doubts until doubts are all gone
2: set a timer for ghusl like 10 mins or 7 minutes
3: try to focus dont think too much on it
4: ignore the waswas it can be a type of worshiping shaytan
ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ ابْنِ مَحْبُوبٍ عَنْ عَبْدِ الله بْنِ سِنَانٍ قَالَ
ذَكَرْتُ لابِي عَبْدِ الله (عَلَيْهِ السَّلام) رَجُلاً مُبْتَلىً بِالْوُضُوءِ وَالصَّلاةِ وَقُلْتُ هُوَ رَجُلٌ عَاقِلٌ فَقَالَ أَبُو عَبْدِ الله وَأَيُّ عَقْلٍ لَهُ وَهُوَ يُطِيعُ الشَّيْطَانَ فَقُلْتُ لَهُ وَكَيْفَ يُطِيعُ الشَّيْطَانَ فَقَالَ سَلْهُ هَذَا الَّذِي يَأْتِيهِ مِنْ أَيِّ شَيْءٍ هُوَ فَإِنَّهُ يَقُولُ لَكَ مِنْ عَمَلِ الشَّيْطَانِ.
Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from ibn Mahbub from ‘Abdallah ibn Sinan who said: “I mentioned to Abu ‘Abdillah (al-Sadiq) (عليه السلام) a man who was afflicted with doubts in his ablution and prayer (constantly repeating them) and added that he is an intelligent man.” Abu 'Abdillah then said, ‘What kind of intelligence does he have, when he obeys Satan?’. I asked him, 'How is he obeying Satan?'. He replied, 'Ask him about this which he is doing, from which thing is it. He will certainly say to you, “It comes from the work of Satan.”