Cramping at 37 1/2 weeks

Hi all,
I am pregnant with my first and am 37 weeks 4 days. A few times in my last trimester I have been dehydrated and gotten what feels like menstrual-type cramps. They have always gone away within an hour or two and with lots of water. Yesterday I must have gotten a little dehydrated (I drink TONS of water but must be really sensitive) and have had menstural-like cramps since then. They were really bad for about 1-2 hours but subsided in the bath and with alot of fluids. Now they are just low grade, but are still here, which has never happened before. They dont' seem to be going away with anything - movement, rest, fluid, etc.

They are separate from Braxton-Hicks, which I have been getting since 20 weeks because my baby has been very low from the beginning. There are no other contractions and my BH haven't increased or anything. I am also not really feeling back cramps or anything in my legs. I haven't lost my plug or have any blood or leakage.

I am wondering if anyone has had this before or has any suggestions, information? I don't think I will call my midwife unless the cramps seem to get worse.

Thanks in advance!