Probably wouldn't be anything terribly drastic. I would depend on what problems your bp is causing you in school. For instance, if you sometimes feel volatile or anxious and the ability to quietly take a time out of the classroom for a few minutes might help, the 504 accommodation would simply say something like "student may ask for time out if she is feeling anxious." There would probably be some conditions about where you could go, who you could see for help, how much class time you could miss, etc. I've honestly never had a 504 student for mental health issues. Usually I see 504 for dyslexia, adhd, and some physical handicaps that just require basic, common sense accommodations in the classroom like hearing aids, special furniture, etc. 504 accommodations generally aren't nearly as extensive as special education accommodations.