If you have had depression a while, go to a doctor and get that sh*t sorted out. (This is a big case of do what I say and not what I do, btw. However, once my insurance goes through, though, you better believe I'm getting out of this cycle. It's hard on my friends, it's really hard on my husband, and it's hard on me.)
The low lows pass. The cycle won't until you are proactive and do something about it.
Pay attention to this. It's very good advice.
Do not self-medicate.
Do see a doctor. And, I'll add.....make sure the doctor really understands where your head is at. Even doctors will sometimes write off depression as something like "the blues". Make sure the doctor understands this has been going on for awhile.
sorry if you've posted this information elsewhere, or if it's something you don't wish to discuss.....have you talked to any family members about this? Maybe your mom, or sister, or someone, might be willing to go to the doctor with you to help advocate for you.