My therapist said that drug abuse creates chemical imbalances in your brain that mimic the chemical imbalances caused by bipolar disorder. He said there's really no way to tell if you're BP or not... unless you have a clear history of sustained mood swings that occurred when you were sober (or maybe you have a relative who has BP). Usually you have to treat the addiction problem before you can correctly diagnose someone as BP.

If you've done a mood disorder questionnaire or you've talked to a mental health professional (namely a psychologist or a psychiatrist), they will ask you are abusing drugs. If you're abusing drugs, they're technically not supposed to diagnose you as BP unless they have good reason to.

Did you have a history of mood swings before you started abusing drugs? When you were sober, did you still have mood swings?