It could be the baby. The first time I felt my first one, it felt like little pokes, nothing like flutters. If it doesn't move, it's probably not gas. Gas tends to move. The baby often concentrates on one area.
Sounds like stretching. The further you get, it gets slightly worse. Im 16 weeks and still get odd pains, bub geels sort of like popping bubbles :) and for majority of other ladies they say it feels like flutters.
I'm due October 3rd!!!!! I think it's movement because i feel the same thing (: