How did you know it was contractions?

This is for those that are laboring/ have had precious children!

My OB essentially told me “you’ll know” when I asked how can I tell the difference between Braxton Hicks/ baby moving against a nerve/ cramping/ contractions. Basically said if I have to question it, it’s not a contraction.

I’ve had the textbook- starts at upper belly, wrapping around back, took my breath away for a couple seconds- contraction. But I did questioned it since it’s not consistent.

So my question is, how did you know?