I would set up an appt to have him neutered. Personally, I wouldn't let him hump. I sturn "NO" or when mine do something I don't like I do that chuh sound, and take the toy away. Especially something like you leg, say NO! and pick him up and redirect his attention to another ummm...activity.
You definately want to nip this in the bud, get him neutered.
__________________  Bella (I miss you)  Sachi Emmy |