Braxton Hicks or contractions

I haven’t had Braxton Hicks since my second trimester and it was just light tightening in my abdomen... for about a day now I have had what feels like really bad period cramps in my back. Nothing up front it’s been constant sometimes it gets worse. I have been trying to rest but I can’t get comfortable I can’t sleep because it is getting very uncomfortable... is it just baby getting into position? Is it Braxton Hicks? I’m laying down and still hurting. I mean just like my bad period cramps. And I’m drinking water... (I’m 37 weeks)