I find I get a lot fewer stomach aches since I've been on SW; I used to have pretty much constant indigestion.
If you're feeling worried about your tummy aches, perhaps keep a food diary and note down when your pains come on? Then you might be able to spot a pattern. (With me, for example, I know that if I eat more fibre than usual, that usually upsets my tum.)
Another thought: have you been doing more exercise than usual, or doing sit-ups? I find a food-related stomach ache can often be indistinguishable from a strained/overworked-muscle stomach ache.