Is it the O? 🤔

So this question has been in my head ever since I've been actively sexual. (I'm 20 btw I know this sounds like a middle schooler question but I was a late bloomer)
When my partner and I have sex, sometimes (very often) if he hits my cervix hard enough or if he goes fast enough, I lock my legs up and start shaking. Is it the O?
It feels good and all but it comes to a point where the feeling gets too overwhelming and the reason why my legs lock up is to get him to stop for a second (which he does). My partner tells me that's me cumming but I've also heard of women cumming through squirting, and by how other ladies have described squirting it's a different sensation than what I experience.
So is it really an O? Are there more than one ways to orgasm vaginally?