Contractions and bowel movements??

I think this may be crazy to ask but either I'm getting bad bowel movement pains, that feel like tightening in my lower back and stomach or these are contractions But as soon as the pain stops, I have to go #2 So could these be contractions? They aren't consistent. And after I make a bowel movement they stop. I haven't felt this pain before though which is why i think they could be contractions. I'm 36 weeks today. Has anyone experienced this? What was your experience with this?