Should i tell him?

I've been friends with this guy for a long time after we collaborated on a creative project, and lately hanging out with him has been messing with my head. We joke all the time and act like regular friends, but the other night we stayed late talking after everyone else had left and it was just way too comfortable to be alone with him. Now I don’t know if I’m getting feelings because I really like him or if it’s because he’s the only person who makes me feel calm in that way, and I’m scared that saying something might ruin the friendship entirely