Hard belly!! Can anyone relate?

So I've been experiencing my belly being really hard! At first only on my right side close to my belly button, but lately my entire stomach has been very hard! I am 31 weeks & this is my second pregnancy. I can assure from my first experience this did not happen :( kinda scares me, but baby is moving a lot so that's a great sign. The pain of this hard belly not so much... Can anyone relate??