Belly always feels rock hard nearly 39 weeks

Jo
My belly always feels hard for the past week like when you get a contraction.. but even after I have a braxton hicks my belly still feels hard now it just won't go away. Impossible to get comfy feels like I'm carrying around a rock under my top. Is this normal at 39 weeks? Was worrying baby was outgrowing my uterus which is what's causing it to feel hard. I doubt it's contractions that I don't know about as when I get Braxton hicks I can feel them.