if you guys are getting that pulled muscle feeling, it might be related to the stretching of the abdominal muscles... I've started getting the lecture about the correct way to get up from lying down while pregnant and we're supposed to start doing that (roll to the side, don't sit straight up).
Apparently with the muscles being pushed forward, you can do some serious damage if you sit up from a lying position.
I think we're still supposed to be technically ok now, but it gets much more fragile later on and if you're getting those pulled muscle feelings, it might be your body telling you those muscles are fragile and to slow it down/do the roll thing?