Get your butt to an urgent care. They can best do a basic evaluation to see if it's something serious, especially because it's getting worse. You don't want to wait until you're unable to move. The worst thing that happens is they say it's a strain and give you some muscle relaxants to tide you over for a while. (Actually, the real worst thing that happens is that they dismiss you because women's pain is more likely to be dismissed. Ugh.)
Good luck and take care.