I had a tubal ligation on 7/17/12. i had to 2 negative pregnancy test and 1 positive. i have had recent stomach and pelvic pain. should i be worrie?

Yes: It could be an ectopic pregnancy (pregnancy outside the uterus) which is a dangerous condition. It could also be a "normal" pregnancy. Tubal ligation can fail. You should see your obgyn as soon as possible and have blood work to confirm pregnancy.

Tubal failure: Tubal ligation like all surgeries has a failure rate. That rate is around 1 in 300 and mostly due to something called a tubal fistula. Anytime you burn, cut or clamp a tubal structure, you may get a fistula. If you had a positive test, go see an ob/gyn asap as a tubal pregnancy is fairly likely.