I have dealt with both issues. At one point I was medically treated for depression. I am currently off meds, but I am still not a 'cheerful' person. (I sort of think of myself as melancholy). I have been through therapy (which is mandantory with meds, meds alone can not treat anything.) Part of treating either depression or anxiety (and they are usually intertwined) is learning how to change the way you think and react to situations. Yes, both disorders have a medical base, but changing the way you look at different scenarios is a big step into treating either disorder.
Treatment tends to be a long term commitment, but worth the effort, and there will be a considerable (and at times, overwhelming) effort required. It can be done, you can do this. Find a GOOD doctor (my first was a candyman - just take a few of these when you don't feel good....FAIL) and follow his/her instructions to the letter. Make sure you keep a journal of thoughts, feelings, reactions, etc and make sure you make all your appointments - no matter what.
I feel for you, it's a hard place to be in, but there is a light at the end of the tunnel and it's not neccessarily the train coming at you (sick humor, I know). Hang in there - you can beat this, or at least, learn how to manage it.
Best wishes.