Have you tried medication. Also maybe once you got a job and a place of your own things would seem brighter.
Also people don;t like being around people who are down on themselves and that could have to do with your friends leaving.
I had really bad depression/nervous breakdown a few years ago and have been on paxil since about 1999 ( I am only 25yrs old) what we found out was I was born with no seratonin so it waskind of a chemical imbalance making me the way I was.
A lot happened in my short life that I thought I could not handle and after really trying to die (i have horrible scars now) I finally got some help.
I now have my own home, a great job (well I am on maternity leave as I am expecting a lil boy in a couple of weeks), a great boyfriend (who does not abuse me because I know now I am better than that) and everything in my life seems great. I have close friends and don't associate with the scum I used to.
Anyway, check out your options, get some help, see if it's an imabalance and see if there are meds out there to help you.
Good luck.