Contractions?

Hey there! First time mom here (39 weeks) and am in need of some help! I just woke up with constant period like pain, very achy but not so painful. But I am also having shooting aches down my legs and up my back every now and then and I am feeling slightly naseous. I'm not sure if these are contractions.... everything seems to be constant and in no pattern. Pretty manageable but definitely uncomfortable. (exactly like how a mild period would feel for me)

My question to other mamas out there is if they started labor like this or if they went into labor soon after similar symptoms? I'm not able to time anything since it all feels like just one forever long cramp.

some extra info: I have been at 4cm 80% effaced for 2 almost 3 weeks now so I know my body is getting close but it came at kind of a surprise since I haven't been able to notice any contractions I've apparently been having so far.

any experience or advice with this would be greatly appreciated!!