Hi there, I'm not sure whether there is any connection but my male pup at the age of 7 months started to became sexually mature. This is when he began his humping of anything including my 3 year old son on a regular babsis, and also started to displayed dominance. Now this may not be connected at all or it could be that he is coming of that time where his hormones are changing and it is affecting his behaviour slightly. Have you had him neutured or thinking of having him done? I notice you also have a young baby in your profile picture, Im wondering if its a competition for your attention over the baby maybe?