Am I asexual? Or just... tired?

I've been wondering this for 2 years almost, but I can't seem to find any answers.I have sexual compulses. I masturbate, I get hard thinking on cute/handsome dudes. You get what I mean.But then it comes to sex and... I dunno. I get hard, but just moments later I lose all my sexual lust. Not like exhaustion, not boredom neither, but it doesn't feel like I'm enjoying the whole thing. Never been with a guy I actually "loved" or cared, just random dudes. Could be that too, I guess, but still I don't know.