I don’t think it had anything to do with the alcohol. Alcohol for women is more likely to increase your desire for sex.
I think the key word here is that you “used to” have a crush on him. Past tense. You just weren’t into it. Thinking a person’s good looking is VERY different than being attracted to them and/or having chemistry with them. Maybe you just realized you weren’t that into him after all. There’s nothing wrong with that.
It sounds like he just wasn’t doing anything for you. Also, because you’re not that experienced with sex, it’s likely that not only were you not feeling anything for him, but you were also apprehensive about the whole situation and you didn’t feel like you were ready for something like that to happen. You tend to get your guard up that way and that puts an immediate stop to sexual arousal.
Either you didn’t want something to happen (weren’t ready for it) or you just didn’t want it to happen with him. I really don’t believe that alcohol had anything to do with it.