I'm only 27 weeks so really hoping this isn't what I think it is.

I've been having Braxton hicks all day. Nothing consistent or anything, but they've come and gone all day. I just woke up from a nap and I have pain wrapping from my lower back all the way around the bottom of my belly. It doesn't come and go, it is constant, so there's nothing to time. I've tried feeling my belly to see if it hardens, and it is hard but it doesn't relax it just stays tense. but nothing I do is relieving it. I'm in a hot shower right now and it's doing nothing for me. I've been drinking water throughout the day. I have not noticed any strange fluids, so my waters haven't broken.

Does this sound like pre-labor or just a bad case of third trimester back pain?