I had the same problem years ago when my world fell apart. I got help from a psychologist. Luckily, I found a good one out of the yellow pages (Some are not so good). The medication will help, but you need to deal with what's got you down and seeing a professional is the best way to go.
What I found was just getting going was the hard part. Once I got moving, it was easier to keep moving. I had to take things in extremely small steps. When I say extrememly small steps, I would say:
I'm going to roll over.
I'm going to sit up in bed.
I'm going to stand up.
I'm going to take a few steps.
I know how that sounds, but I was very depressed. As I did that more and more, it got easier.
You're holding a lot in emotionally and you are in a lot of pain. You have to talk to people to get it out so you can... cry and begin getting some of your troubles behind you and in perspective.
Talking in this forum will help, and I advise you to do so a lot. I think it's more important that you see a professional you can talk to.
Set some small goals every day. Actually make a list so you can check each one off. It shows movement. Make sure the goals are achieveable. So start small. Once you do that, you can go to larger goals.
When I was going through the toughest times I kept a journal. It would let me get some of my thoughts and feelings out and on paper. Just make sure you don't use the journal as a club beating yourself up. It's purpose is to help you deal with your situation.
Realize you are not alone. I remember when I was in group therapy realizing that I wasn't the only person in the world having problems. Before that I felt so alone and that everyone else was living easy productive lives. That wasn't the case. No one escapes tough times. But it's so easy to assume that no one has the problems you do. They do.
Direction determines destination. You've got to start moving in the right direction. Actually, you've taken a very good beginning by coming to this forum. You've got a long way to go, but each step will bring you closer to a better life.
All the best.