39 weeks lower back pain

So I woke up last night with a hard belly and lower back pain. (Baby has been partially engaged in an almost back to back position for a few weeks) I got up and rolled around on my birth ball before going back to bed with a hot water bottle.

All day today I've had lower back pain and a hard lower stomach on and off. I went swimming which was lovely but I just didn't feel settled I just kinda floated around at the deep end watching everyone rather than swimming(it's the pool I work at as a casual lifeguard and have practically lived in the pool my whole pregnancy).

The rest of the day I have spent on all fours huffing and puffing then bouncing on my ball or going for a shower or walk!! I feel funny like not myself.

I haven't had any contractions just a hard lower belly but it goes Rock solid for about 30 mins at a time and doesn't change if I move position. This is how it has been since about 20 weeks!

I'm so knackered what's going on!??