I also have this. Around my belly button there is a 5cm x 5cm area of skin that had no feeling at all.
I guess it's just the skin stretching over the nerve endings - and the nerve endings don't stretch so we can't feel them in some areas.

It's weird though, because I get an itchy belly in that area but when I scratch it, it does nothing...... soooooo frustrating!!!!!! I sometimes ask bubby to give me a scratch from the inside..... doesn't work though

S X