Why doesn't sex interest me? (18m)

Sorry not sure what subreddit to post this is in but hear me out.:I feel like anytime I've ever hooked up with someone I'm very good at pleasuring the person I'm with but while I'm getting head or kissing I'm never aroused, like not even a little. I find myself complete soft and my mind wanders to random things as if I'm bored?And after I cum I have absolutely no interest in the person in front of me. I thought I might be asexual but that can't be it because I watch porn and I do enjoy watching someone else receive pleasure I'm just so confused because I can't figure out why I'm not sexually attracted to anybody.