Is this labor starting or just normal...

I havent slept all night because of pain in my lower abdomen like a full on period. Not contractions because it hasn't gone away and come back or anything and it hasn't got worse but it's just been a constant ache that's kept me awake overnight. I went for a walk yesterday and initially thought it was maybe just sore from that but it wouldn't last all night. The only way it goes away is when I'm walking/standing and then if I sit or lay back down it comes back.

I'm 38 weeks 6 days this morning