Hey man, I'm sorry to hear about the situation you're going through. You need to identify the triggers that lead you to relapses.

Also, when PMO thoughts come to your head, swat them away and think of something else. Don't let them continue luring you in.

Also, I would suggest reading this book, "Why my brain isn't working", which may help your situation with studying (I wish I knew this when I was in school). You can check it out here: https://www.amazon.com/Isnt-Brain-Working-revolutionary-understanding-ebook/dp/B00D8N6HBM/

The TL;DR of the book is that your brain and gut are connected and rely on each other. Modern diet consists of high sugars which deteriorates the brain and causes fatigue and brain fog. I used to be a nootropic junkie but no longer need that crap to focus.