It's still early yet , give him some time . I didn't have my Scooter neutered till he was 6 years old . He never marked in the house till my daughter brought over a male boxer she was dog sitting . Then the little bugger started it .After I had him neutered he stopped . I did keep him leashed to me for a while afterward so he couldn't sneak off and do it when I wasn't watching .
Hang in there it should get better soon .
Bren~N~Cami |