Braxton hicks or cramps?

I'm 31 weeks and today at work I got really bad cramps, kind of like period, kind of like I was about to have diarrhea. It was my whole stomach and not just the lower part like with normal period cramps. But my stomach didn't tighten up like people say happens. FTM so I'm not sure if these were Braxton hicks or just cramps? It only happened twice and only for a few seconds.