I think I'm bipolar..but am being treated for depression..need some help?

I've been on zoloft since I was about 15 (22 now) and at first it worked. In high school I did a bunch of drugs and during an adderall/coke episode I got into some trouble and it was either get arrested or go to a psych ward. They diagnosed me as bipolar, but at the time I was so high and manic from the drugs I figured they were wrong. So I've just been on and off anti depressants ever since, but I'm still depressed. I also experience the highs and lows, one day I'm invincible and don't have enough hours to put all of my amazing ideas into effect..the next week I'm suicidal. I pretty much know that I'm bipolar, but I'm terrified to face it because I don't want to be crazy...but at the same time, I want to fix it with the right medication. Does anyone have any advice or insight about bipolar? please help I'm so confused..