Stomach tightening .

Cynthia • 20, engaged and ttc.
I know that when your stomach tightens for a few seconds and let's go those are supposed to be Braxton hicks. But I have had this happen more than just a few times today and I'm starting to get worried. They don't hurt or anything . But they're definitely noticeable and uncomfortable. Should I call my doctor or what ? I'm 28 weeks.