Whoopy, I completely sympathise with you. I am almost 23yrs old and in exactly the same position. I have never known what I wanted to do, don't really have any valued interests or skills, so consequently I am stuck in a dead on job with c**p prospects. All I know is that from a very young age I have always wanted to be my own boss and/or work from home. I have done both of these twice and loved every bit of it. But either come across problems or got bored. Now I am married, trying to plan a family, but feel completely useless because I can't seem to do either because I don't feel I have earnt that priviledge.
This probably reall yisn't helping you and I know I found it very depressin ggetting the same comments, but I think the key is to try a bit of everything, search your soul for something you really enjoy doing and going from there. Always remember to think of the good things you have, as it is always too easy to concentrate on the negative.
I really hope things work out for you, all the best x