Contraction or not?

Hello all. im 37 weeks now. today feel pain/sharp pain at my lower abdomen area, especially after i move about slowly. Also when baby moves, my tummy will feel tight/conraction feeling. I will also feel like I want to poop. Is this contraction or just my uterus expanding? Not too sure what am i feeling but its quite uncomfortable. I also feel a dull aching pain at my lower back.