Could be your body ramping up for the big day. If you notice a pattern to the cramps and hardening then more than likely it is contractions. And you can feel those in different areas. Sometimes I feel them in my hips but not my belly. With baby number 2 it was all in my back. So the where is not as much of a flag as you would think. I know that isn't a lot of help. Sorry
I'm almost 37 weeks... But baby weighs 7lbs already lol
When your having contractions your whole belly will get tight and if its active labor it will do that more frequently and start to get more painfull. You can loose your plug days or even weeks before labor. How far along are you?