As far as I know, there are only 2 sex scenes but one of those is where he'd end up hating you (Black Heart route). The more "canon" one (and only one atm) you can get is from the "Troubles in the Den" event. There's a variant of this as well if you remained a virgin all throughout the game prior to this event.
Though there is also one scene where you can sniff his pits but... is that... considered a sex scene? I thought it was pretty sexual lol but then again there's no penetration or cumming there so I guess not.