Please help, everything seems to worry me, and yet I don't have much emotion?

I get really nervous about going out, even when I'm meeting people I've known for years I tend to avoid it and just want it to be over. I'm getting less and less social. I've been staying at home quite a bit since uni ended for the summer. I was looking forward to the end of the exams because I could go out more and meet my friends but now I feel they don't even like me and I just don't want to see anyone. I play games at home and I'm feeling less emotion, normally when I play my video games I get really emotionally involved but now I feel nothing. I can't remember the last time I was genuinely happy or moved by something I read in the paper. When I do go out with my friends it's just out of obligation and I don't have a good time. Sometimes I don't even know why I exist, I feel like a burden to everyone and no one really knows me even when I try and open up and show my true character they're not interested. I'm becoming more introverted and I just feel like a robot.. Any advice?