What does an orgasm feel like??

I'm 21, been sexually active for 6 years and have never had an orgasm. Today I was having sex with my boyfriend and it felt SO good, all I could think about was the pleasure of the sensation and my mind went blank for a moment and my muscles started trembling and contracting. Did I orgasm?? I didn't feel my vagina muscles contracting or that feeling like I need to pee or anything that people usually describe, and to be honest it was slightly underwhelming from what I thought it would be. But my boyfriend says it seemed like I came, and I haven't had a feeling like it before. Can someone explain what an orgasm feels like??