bluebicycle, I'm sorry these scary thoughts are haunting you. I can imagine if I believed this of mine that I'd be quite upset. Have you told anyone else about these suspicions besides us at PC? I think for your sake it would be a very good thing to do.
I think staying on bipolar medication is very important. I fear if you only take a stimulant you could become very ill. An idea that passed my mind, at least in the short-term, is consider going to a different pharmacy and asking them to call your current one to transfer your prescriptions. I assure you that most all pharmacies are on the up and up. You could even ask the different pharmacy to inspect your medication.
Hugs