Abdomen Pain After Walking

MUByM

I've been going walking everyday since Jan 1st for at least 30mins. Recently I upped it to an hour and I noticed that my abdomen gets very sore. It's been about 7 hours since I came back and it's still very sore. I'm sitting at the computer chair and with every body movement I make I can feel the soreness. Also I walk pushing a stroller with my son in it the whole time.

Anyone have an idea of what it could be??

Thanks in advance!