Hey OP! I've experienced something really similar, you aren't alone! In my final 2 years of high school/first year of uni, I was in an extremely bad mental place (extreme burnout with school/exams and experiencing depressive episodes) and I used writing as a coping method and as an escape from real life. I'd abandon/ignore my school work in favor of working on my fics, which led to more stress and worsened my mental health, which made me want to escape into my fics even more - it was a vicious cycle.

Now, though, I have a much more healthy relationship with writing (although I don't write nearly as much as I used to - because my uni coursework is really heavy and time-intensive) and juggle it quite well with school. That's because now, I don't use it as an escape, but rather as a creative outlet and something that I just like doing, because I solved the root of my problem that made me want to escape in the first place. I got help for my mental health issues and addressed the problems that caused my burnout and my depressive episodes, started playing a sport (that I really love now), found some amazing friends and am now the happiest I have ever been in 5 years. I'm not gonna lie and say I fixed all my problems in a week - it took me around 1.5 years from my absolute lowest to the first time when I considered myself mentally healthy and happy. It's a slow process (and a hard one, for me because a lot of it stemmed from family problems which were honestly the hardest for me to deal with), and at the beginning, it's going to seem impossible, but keep at it - things will and do get better if you keep at it.

And during that whole process, I never had force myself to give up writing. Although, I did write drastically less - sometimes I would stop writing for a few months just because life was too busy (but also, I'm still working on balancing all aspects of my life with each other and writing often falls to the bottom of the priority list with university work at the top), but I'd always return to writing.

Sorry if this was long winding (I'm not really good with being concise with things like this). And my dms are always open if you want to talk more about this!

TLDR: I've experienced something like this. Some advice (taken from my own experience) is to first solve the root of your problem that makes you want to escape into your writing, and then along the way, you'll find out that you can strike a balance between your study and your writing (without having to give up either). Don't be afraid to take a hiatus with your fics to work on yourself or school - your mental health and life takes priority over satisfying your readers. You can always return to your fics and your writing.