My doc told me signs are regular contractions (more than 5 in one hr), cramping, diarrhea, back pain, pelvic pressure and decrese in fetal movement. Sounds like it might just be part of your pregnancy but you never know call your doc if things get worse or youre concerned. Labor is different for everyone good luck
You shld go in especially tht far along it sounds like labor to me
Oh and I'm 36 weeks by the way so let me know if this is just normal for this stage of pregnancy