Do you exercise?
I had the exact same problem as you when I was at about 7-8 month post
partum. I remember coming to this board asking the exact same question.
Some responses were that my stomach was bigger from the "yuezi" and that my
stomach could be dropping.
I started exercising about 2-3 months ago (not to solve this problem but
just want to get back to my normal weight) and lost about 5 pounds since
then and suprisingly this problem is much better now. I still think I'm fat
but I don't think my belly is any fatter than the rest of my body like how
it used to be.
I'm not saying that this will resolve your problem too, as it could be just
a coincidence but if you are still heavier than pre-pregnancy time, maybe
you can try some general exercising. I didn't even focus on my belly. I
just run eliptical machines but I think general exercising and dieting can
help you body in many positive ways.