Hi L.,
I'm a single mom (one 6yr old son) and I can totally relate! I'm not in school, but I work full time and live on my own with my closest family living 830+ miles away.
It's hard to carve out time for yourself but it's definitely something you should try doing. If every week is too much, then maybe you could get away once every other week or once a month. Your outings could be alone or with a friend. Maybe your parents could take the kids out for awhile and leave you home alone for a bubble bath. If you like to read, you could go to the library by yourself and find a book you want to read and get started on it while you're there. Meet a friend for lunch - either at a restaurant or at their house if you dont have the money to eat out. Join some sort of club that meets monthly to cultivate an interest you have beyond your children - you will get to spend time with like-minded adults which might halp with feeling anti-social.
It also might help you to speak with a therapist. If you have health insurance, you can find out from them what kind of mental health benefits you have. If not, the state has a program for mental health () more info: http://www.dhs.state.il.us/mhdd/mh/)
Becoming anti-social is pretty serious.... I've been that way for a few years and now I see my son picking up on my habits... and it's making it hard for him to make friends. I'm seeing a therapist to help me deal with it, and one of the things she suggested is that I force myself to say hello to every person that I make eye contact with. This will make me appear more friendly and outgoing, so other people are more likely to respond, which helps to break the cycle of anti-social behavior.
Good luck with however you decide to approach this issue :)