Maybe the start of something?

36w6d today. I went to take a bath, within 5 minutes of sitting in the tub baby boy started moving ALL over the place. Which made me feel like I had to pee, so I got out and peed. Once I got out I realized my stomach was so hard (harder then it normally is) and more roundish? My fiancé says it literally looks like a balloon that's going to pop. I've been having slight cramping, nothing too painful but noticeable. Just find it weird how my stomach changed its appearance within 5 minutes. Anyone else experience this?