Ok, for what its worth here's my take on the situation.
Like you I suffer from SA, Low self-esteem, depression as a result of the former, am terrible in social situations, have little hope for the future, but I'm 35.
I'm not sure what you do to combat your problems, but wallowing in self pity will get you nowhere.
Have you ever heard of the saying the definition of madness is doing the same thing over and over and expecting a different result?
Girls will not come to you.......ever, unless you are visibly wealthy or a celebrity, therefore you have to give yourself some worth.
One thing you can do, that costs nothing, will make you feel 100% better, and is a good first step on the road to recovery is exercise, trust me on this.
Start out gradually ( say 3 times a week ), and increase to 6 times a week, variety of exercises, eat well, and try and adopt the mantra "healthy mind in a healthy body". Hopefully this isn't too "jock" like. If you need an exercise plan, PM me. If you catch the exercise bug, it'll change your life.
However regardless, you must find something constructive to pass your time, give yourself goals, achieve things, just don't continue along the same path, you will not change, grow or get better if you do.