why am i not into it?

I’m 17 and i met this guy in the beginning of the school year, we started talking and i finally went to his house to “chill”. Two of my other friends (they’re dating), came over as well and did they’re own thing in the other room. My man and i we’re making out when he pulled me on top of him and we started grinding. After doing that for two-three minutes, he unbuckled his pants and i felt his hard on and at this point i’m not into it. It’s the first time we’ve done anything and i wasn’t comfortable enough. I felt what he was doing but barely, it was almost as if i was numb. He was having the time of his life and i couldn’t seem to let loose and be comfortable.