SIT UPS?

So today i feel like i did a million sit ups however, i didn't even do one. I think my tummy is getting pressure from the baby and is stretching. It is a crazy feeling and becuase i have never been pregnant before this can be my only explanation of a sore tummy. My pants are starting to not fit as well. The begining of pregnancy is interesting. But i still can't wait to be a mommy!