I'm finding the same. My belly looks dry, esp near my belly button but I dry to keep it moisturised.
Also, don't forget to hydrate from the inside. Drink plenty of water and use lotion (the non perfumed kind, as they can dry skin out even more.)
It's skin stretching and dryness. Try to turn your shower to cool before getting out, or try an oatmeal bath. If those don't help or its bad enough that you are breaking the skin talk to your dr.
I have the SAME issue! I have no idea what it is at all though so I hope you find out!