I urge you to seek help. Crack open the phone book and call a crisis hotline; There are plenty of free services to help you deal with problems and depression. Stop by a church and ask to speak to the pastor/priest; You don't have to convert or join, but men of god can often give good advice and are generally good listeners. I recommend a catholic church...they're less likely to try and get you to convert or join up.
Whatever you do...don't dwell on whats wrong in your life. Realize that things could be much much worse and that compared to most people on this planet you have it pretty damn good.
At 23 you're very young and, allthough you don't know it now, still growing up. Don't take that the wrong way. I say that from experience and with sincere hope that you understand what I mean. Hell, at 40 I'm still learning and growing up in some ways. Thats what life is really about...learning from experience and gaining wisdom and maturity along the way. Whatever doesn't kill you makes you stronger.
I've been where you are and lower/beyond that. I've been cheated on, divorced, screwed over by "friends", arrested, locked up in mental wards, diagnosed with depression, contemplated suicide (quite a few times), bankrupt, burned (fire), wrecked more cars than you can shake a stick at, shot at, stabbed, fired, beaten, unable to see my kids for a short time (the bitch moved away with them), hungry, lonely, homeless, ...well, the list goes on, but you get what I'm saying. My life still isn't perfect and, honestly, it would be boring if it was. I'm still learning and growing and, damnit, thats a good thing!
Learn from your experiences and try to make lemonade out of the lemons life deals you. It might not always work out for the best, but you can say "I did my best!". That's more than a lot of people can say.
"To thine own self be true" That might sound like a cliché, but its true. Before my grandmother died at 83 she left me with this gem of wisdom: "If you're my age and have one true friend...you're lucky"
Well, I'm rambling it seems. I hope things get better for you and wish you peace and serenity. Please seek help for how you're feeling. There's no shame in it and there are plenty of places to get it.