Chances are most companies will reject you on sight stating a pre-existing condition (ADD). The state of health insurance is dire, with companies raising rates like crazy and turning down everyone they can.
In any case, find an insurance agent in your area. Not only does it give you someone local to talk to/answer your questions but they can probably give you quotes for several companies, including any that may allow you to enroll.
As a last ditch effort, see if your state has some sort of Major Medical program -- these are typically state-funded insurance programs for "uninsurables." Caveats: it is expensive, but usually less than what you're paying for pills. You must also have proof that you've gotten declined coverage, so you have to apply for insurance anyway.
Your best bet is to get into a group insurance policy -- you state that your school's is crap; make sure you're positive that they won't cover your pills, because they'd be your best choice. If you don't have a job that offers group benefits, find one. It will be substantially cheaper than major medical.