Don't worry about your past.
If you're more than willing to change the way you live now -- which I'm sure you do -- you could try to work on what you CAN change about it.
Life is all about learning, and you are doing exactly that -- no matter what your age is.
If you want to be happy, then start putting the effort into building that happiness -- starting with working on getting what you actually want.
Just put yourself out there and meet new people and be open about yourself to others!
You might be surprised with the people you meet! You may even find a new girlfriend!
We are the social creatures of this world, and there's no escaping it.
I say, you go out and try again. You say you're not in the best shape right now, perhaps you need a friend or mentor to help get you through it; but nonetheless, try to have an optimistic outlook on what's to come of the future of your goals, and to emit a positive energy to your surroundings.
Life is all about effort to building good things and you know how destruction comes so easily.
You will draw in more people when you're happy than when you're upset, and if you think nobody cares anyway, you might as well try to be happy!
We can talk more if you enter the chatroom sometime -- I come here regularly to help others, so don't hesitate to join in!