[mscat]

On a few of It's Me Or The Dog , Victoria Stillwell has come into homes where families have had dogs with extreme aggression issues, much like you have described in your Yorkie puppy. In these cases , She has taken these dogs, along with the owners to the vet. Checking for specific medical reasons that could contribute to dog agressive behavior. One that I remember was Thyroid disorder. I would have your vet due a CBC on your pup and ask about what other medical conditions would cause extreme agression in cannines .
Rocky needs to be tested for them. This might not all be behavioral . Especially , because his aggressiveness has occured at such a young age + he had been fine for the first couple of months you had him. This makes me supicious that their could be medical implications that need to be addressed.
I know how difficult it is to try and balance your own medical needs and then trying to handle a pup who has turned into a unbalanced , biting, unsocial , creature. I am on complete disability myself . My Yorkie was quite young the first time I had to be hospitalized, when I came home she was all over me, was not scared at all. She actually licks my pain away .That is how sensitve she is. She also stayed with me in my bed when I could not get up , never leaving my side.
It is the temperment of each dog that comes into play .Not all dogs are made the same way, just like us humans. My other puppy , is very different then my Yorkie. She is more assertive, and will bite , when being brushed, or try taking a toy away from her ! She's 4 months old . I just try to be patient with the puppy, and tolerate her aggressive behavior, and not allow her to think she is in charge .I have been bitten, many times though, and it has broken the skin.
I know what that is like, however , I am working throug it with her. She is not always this way, only during brushing, she is also very Food motivated .This helps me train her and calm her too.
Does Rocky respond to food motivations? This can be a very effective training tool. Starting out slowly, then gradully working up to more difficult training ?
I wish you the best, & hope that something can benifit Rocky and help you be able to keep him . If not , at last resort a Yorkie rescue would be in the best interest of Rocky.