Contractions or something else?

I’m 31 weeks tomorrow and even though I’m sitting still and have been for awhile, playing games with my partner, I just got SEVERELY painful period-like cramps. It hurt so much I couldn’t focus, last about a minute, went away, and came back. I went to the bathroom to check for blood because it honestly hurt so bad I thought I’d have to be bleeding but I wasn’t.

Any idea why that is? This is my second baby and I never had that kind of feeling with my first. Nothing that strong or painful.