I'm feeling cramp-like pains like wanting to go poo at 37 weeks pregnant, but i didn't poo and pain comes and goes (very light pain) but at times more?

Likely contractions: You are most likely having some braxton-hicks contractions (warm-up contractions). The sensation of feeling like you have to have a bowel movement is from the baby's head pushing down in your pelvis when you have a contraction. If these pains become consistent and unbearable, head on in to labor & delivery to get checked out for the possible onset of labor.