New spoo humping

We picked up our 8 week old spoo yesterday. We had spent about a total of four hours with him while he was at the breeders during visits. There was never any humping behavior with his litter mates or the other adult dogs at the home. Now that he is home he is humping everything and everyone. Why would he never exhibit this behavior at the breeders but it’s non stop here? We don’t have any other animals and its just me and my husband. We are using distraction to discourage. Help!