First stop for a minute take a deep breath and take time to regroup. It may be a good idea for you to consult with an attorney who specializes in these matters. Don't just pick one at random out of the book. If you are part of a union consult your rep for a referral.
The facts are pretty bloack and white in that you did have a positive drug test and that you did violate HIPPA so the grounds for your termination are valid. Also if PA is an "At Will" state they can let you go at any time without a reason which many employers in "At Will" states will do.
You employer actually has a duty to report your positive drug test to the BON. They may or may not. My suggestion is you get another job right away anywhere you can, Nursing homes, Psych facilities, telephone nurse with and insurance company. Then cut your expenses to a bar minimum and sock everything you can into savings. Some Boards take up to two years to act on complaints so use that time wisely.
If you are still using marijuana stop now and don't pick it up again. It' messes with your bi-polar meds anyway. Also if you drink alcohol stop that too. Even if you are not an alcoholic you'll have to stop anyway because all board monitoring programs require strict abstinance from all recreational substances and many prescription meds like ativan, xanax, ambian etc...
If you feel you have a drug or alcohol problem get involved with AA or NA right away. Even if you don't believe in the 12-step model of recovery the board will make you do it anyway and if you have some meeting time under your belt they may take that into consideration. Also you may want to look into Mental Health annonymous to help build coping skills with regard to you illness. These groups are all free and the only requirement to join is an honest desire to overcome your addiction/affliction.
Your diagnosis of bi-polar d/o can work in your favor. Make sure you get documentation from your Doctor (Psychiatrist) about you illness and that it makes you unable to work at this time. I don't know if PA has state disability insurance but you may be able to qualify for SSDI under the bi-polar dx.
Most of all keep your chin up and keep trudging forward no matter what.
Write to me here for support - I don't know all the details of your State but can help with general cheerleading.
Peace and namaste
Hppy