How to stop wondering- “what if?”

Hey. I’m 17 F. I was diagnosed with generalised anxiety disorder and ocd (not related to cleanliness) about 5 years ago. Therapy isn’t an option for me right now (my personal choice, not willing to change my mind). But this is seeping into my daily life.

If I’m not worried about something, my brain automatically finds a reason to worry. I keep thinking of thousands of what if scenarios in my mind from the daily things that I do (rn it’s my board exams) and drive myself crazy.

Is there anything I can do to help stop this