It took me years as well to finally be diagnosed with biploar disorder. First they were thinking Seasonal Affective Disorder, then it was depression, and now it's bipolar disorder.
It kind of came as a relief, almost like closure. Like okay, I knew there was something going on with me and now we can progress and try and manage this. I see a therapist every other week, and I'm going to a pill doctor. She has me on Serequil, Lamictal, and Lexapro. And the great thing is that there are so many options and support. If at first your meds don't succeed, try some getting on different meds. Go through psychotherapy, it really does help to get things off your chest, not be judged, and get ways to cope. Check and see if there are bipolar groups you can be apart of, or other groups. I just found out a really good group that I'm going to check out this Tuesday called "Coping Skills."
So yes, it's pretty scary. Especially if your friends and family don't understand it. But there is A LOT of help out there. Just do some research and see what routes are best for you. You're not alone, there are a lot of helpful people here!!
Good luck!