Hi Wolfers
Not sure how to help you more without a bit of general info about your situation (I am very new here - few hours), but please remember about one very important thing. When you get yourself pushed into the dark corner, all seems hopeless cause all you can see is the problem in front, preventing you from thinking about anything not involved with it. What I have found out, is that we have the ability to drag ourselves from those holes, but to start doing that, we need a bit of fresh perspective with glimmer of hope we can cling to. If you have someone you can have an honest talk with, try to get his / her view on your situation. If you don't want to go into details, try to get a his / her response to its more generalized version in a casual manner. I happened to see myself as a pathetic fool, only for my friend to casually point out a few advantageous aspects of my personality and life, with such brutal honesty, that even I couldn't rebuke them. What also helps me is to get some sleep, though falling asleep itself is troublesome. It eases the burden of situation and allows me to eventually get a bit of a breathing room in my mind, so I can create a plan how to proceed forward. Remember that when your mind is tired, depression strikes harder. I know that when you are depressed it may be hard to get a good rest, but aim for it either way. The more rested your mind is, the more clearly you will perceive the situation and solutions to the issues.
You said "I must be terrible". The way I see it it, it couldn't be more different. You are hurting, yet you still worry about hurting someone else. Most importantly, you feel helpless to the point of crying out loud, yet you still find strength and courage to seek help here. How many others would have found that strength? How many others would have thought about other people under such circumstances? How many others would still reach out for help? You still haven't given up, despite the situation. Take pride in that. You are most certainly not terrible, I am a stranger, and I can tell that after quick look at your post.
Good luck. There are people willing to help if you are willing to share some of you problems with them.