I had a tummy tuck in November 2009. This week, I started an exercise "boot camp." (It's kicking my butt but I love it!). HOWEVER, I am noticing that the muscle area above my belly button is now beginning to "bulge" or form a lump after doing ab exercises- and is no longer flat. Why? I much prefer the flat stomach. Shall I avoid ab exercises? Why is that muscle making a ball?