I'm the first to admit that the term 'bipolar' is thrown around too loosely (as well as ADD and ADHD, but I digress.) So many are labeled as bipolar when all they probably need is some damn structure. I hate that.
Anyways, it took years for me to be correctly diagnosed. They just thought I was a rebellious shit for a long time - writing countless bad checks for outrageous shopping sprees, drugs, mood swings, violent tantrums, etc. But finally someone nailed it. My Grandmother had it - but none of us figured I had it too. After reading all the brochures and what not att, yeah - sounded like me.
I don't know if this would be the case with you, but it's a good possibility if you hit up some professional help, they'll immediately label you as bipolar. You might want to put up a little bit of a fight first, sticking with just depression. Oh, I don't know. I'm deffo no doctor, but I do know they're quick to throw the 'b' word to anyone who walks into a shrink's office as a new patient.
But I will say, the mood swings and substance abuse is a common trait of us whack jobs.
If you have any questions or anything, I'll be more than happy to help as best I can. And I hope you do think about getting some professional treatment. Support can't hurt one bit.