Welcome back, but I'm sorry to hear you think your life was worthless. If it was any consolation, even being on here is a contribution to society. You have a ton of great ideas and sharing that with the world is a very good thing.
I do understand though how you might feel. I've found my time here is mostly lurking now (With period of spurts here and there) because I am trying to focus more on what I want to do with my life. I too have had difficulty finding a job, but I am working part time as a Custodian at a school district. I find going someplace for work each day really helps me feel good about myself and makes life worth living.
Anyway, I hope things get better for you but don't feel bad about your life. Live it to the fullest, and make the best you can each and every day. Also, it's great to see you back.