OMG!!!!!!!!!! I can't believe someone else has this!!! I had the exact same thing in the last trimester and my OB said he'd never ever heard of it before and just put it down to ligaments and stuff stretching in there. I usually heard it when i was relaxing and baby would move. It is obviously perfectly safe and normal a my DS is perfect, so don't worry, but its really cool that im not the only one who felt that!

Goodluck with the rest of your pg!