Wowee - that def looks like it could be baby pushing out (but I'm no expert).
Funnily enough, my placenta is anterior this time, and I was saying to a friend how at times I felt like this kid was pushing shit around in my tummy, as I'd feel this hard tension/pressure in certain spots, then it'd disappear. I couldn't see anything from the outside, but that's probably because of the position of the placenta covering the baby. All I can say is, my tummy "felt" like yours looks.. I did wonder about braxton hicks too, but I'm leaning more towards baby...