Your baby is still very low, behind the pubic bone. You're feeling gas.
It's different for ever pregnancy (like pretty much everything else with pregnancy). at 11 weeks, my uterus was well above my pubic bone according to the doctor, being able to feel it, and where baby's heart rate was picked up on the doppler.
Not saying OP is correct, or wrong, but it is possible (even if highly unlikely) that she can feel something going on done there.
Although, I always think I feel something, and then a fart comes out a minute later :/