tightness

I'm 25+4 FTM and I've been feeling a constant tightness in the bottom part of my stomach. I know with Braxton hicks you get tightness, but don't they release? I feel like I did a moderate abs workout. It's not bad enough that I can't take it. it is really bothering me, but not enough to call a doctor. Just enough to want to know what's going on. Is there anything I can do to ease the tightness? What is it in the first place?