dieting exercising and not losing weight

everytime I am dieting and exercising to lose weight I get these unbearable stomach aches…WHY IS THIS!?

It seems that everytime I start dieting and exercising to lose weight I get these really bad stomach aches…does anyone know why this is? Because Im hoping Im not doing something wrong or its something bad :

Hmm, its probably cause your out of shape, it happens a lot to people when your not used to the small amount of food and the large amount of exercise

Don’t worry your fine, it happened to be today too, I didn’t eat lunch and exercised when I came home from school, and I had bad stomach cramps.