How do I know if I’m in labor?

I know this is stupid. But I can’t tell what’s going on my with my body. For about the last 4-5 hours I’ve been having this extreme tightening at the top right of my uterus, right under my boobs. It gets really, really tight. I’ve also been getting “lightening crotch” a ton, so much it takes my breath away in moments. I’m 35+5 today. Is this Braxton Hicks? Is this early labor? I have an OB appointment Wednesday morning, so I’m certainly going to ask then. But I feel so stupid that I have no idea what’s going on with my body. Has anyone else experienced this??