I just noticed this the other day. Every once in a while I feel very sensitive - sometimes its rather painful - where I think a foot may be lurking. I very lightly bumped my belly against a chair yesterday and it hurt way more than it should have. I'm chalking it up to normal for now.
I only notice these when someone is feeling my uterus like when I was going to the midwife. It is like they pinch my flesh between their fingers and the baby. It HURTS! But they said it is normal so *shrug*
I have a small spot on the top left side of my belly where it feels that way, but only sometimes. It's like 4-5 days out of the week it happens, and always in the afternoon and for the rest of the day. Feels bruised, especially hurts if I touch it (I know I know... don't touch it)