The start of contractions or just gas cramps?..

Ftm at 40+1. It just started about 30 minutes ago, but I have a lower back ache and I keep getting what feels like period/gas/constipation cramps.. They aren't intense but they definitely hurt and are uncomfortable. I don't have to go to the bathroom either, I've tried and nothing. I also was over 50% thinned as of Tuesday but barely dilated... I've heard that can change quickly though but I don't know. Also as soon as the cramping feeling starts, the pain in my lower back gets worse.. Any suggestions or idea of what it is? Is it just early labor? Anyone have/had this? 😖😮