I feel like i'm losing my friends and it's my fault

It's not like they're not there for me any more, or that they don't seem to like me as much. It's just that I never seem to be there for them when I want to be. I don't seem to care about them any more, and I don't know what to do about it. When I'm with them all I want to do is be alone, but I feel like I'm betraying them. Things come out of my mouth that I don't mean, and I can't take it back. I feel like I'm losing them, but I really do like them as people and I don't want to not be friends any more. It's really hard to explain and I don't know if I put it down right, but that's how I feel. Is it normal to feel like this about your friends?