only thing to do is test. have you gained any weight recently? i had a tummy tuck and when i went up even 2-3 pounds i felt that stretching. you are supposed to keep your weight steady. (even knowing that, i got pregnant once after the tuck, had a m/c and i am still trying!).
The only way to know for certain if you are pregnant is to do a HPT or have a bloodtest done. You are causing yourself needless worry about an ectopic, without even knowing your pregnant yet. Good luck to you!
If you had a tubal ligation...you're probably not pregnant. take a home pregnancy test if you are concerned. It's probably something else ... are you gaining weight? Maybe that's causing you to feel the stretch.