Braxton hicks vs contractions

I am 36 weeks + 3 days with my first baby!

My stomach has been very crampy at night & anytime he moves I can feel it very very low and it hurts. The other night I had horrible cramping at the bottom of my belly for about 15mins. I sat on the toilet confused if it was contractions or really bad poop pains.

I’m curious if I can have small contractions this early and be very spread out OR if they are just painful Braxton hicks. Please explain how you know the difference. Something in my gut is telling me this baby is going to come early.