Orgasm? maybe?

Ok, I'm curious. because every time my boyfriend and I have sex, I am twitching and moaning uncontrollably. My back arches, I feel like I have zero control over what my body is doing, I grab whatever my hand finds and death grip it he has to hold me down sometimes because of how much I buck/twitch. It all feels amazing, I think it's the big O but I'm also not 100% sure either. because he's my first, and I can never get myself to feel the way I do when I'm with him. So is it a full blown orgasm or is it just me really enjoying what he's doing?