What were your earliest signs of labor?

Moms that went into early labor or labor naturally..what where some of your signs and how much time did you have before you just knew?

I'm 36 weeks on Friday. I found out aty ultrasound yesterday that he was measuring at close to 38 weeks already and low.

Last night I experienced mild period cramps, tightness in my stomach that took my breath away along with in my lower back and some extreme shooting pains in lower stomach into groin area..like literally idk how my child didn't just manage to escape.

I was able to get a little rest last night but now I'm up unusually early with a bad headache and continued nausea (which started last night. )

Just curious how careful I should be if these are early labor signs? This is baby #2 for me 😬