Sam - I'm not a vet, however as an MD with several dogs we cherish, I've had to deal with quite a few issues. You need to get your dog to a specialist, such as a major veterinarian school or high end specialty practice ASAP!. Don't wait. Your vet might be able to make the referral as well or guide you a top specialist, if they are reasonable. I'll apologize in advance for possible disparaging sounding remarks to vets who might be on the forum or for the good ones out there. It is just my experience, where I live.
My experience with scores of my "local vets" has been terrible at best. Most have little basic understanding of physiology and have become mills for selling vaccinations and performing basic expensive tests. They don't practice anything scientific as it is too expensive for the average client, or they just don't understand having spent time studying horses to ferrets. The nonsense I have had vets tell me over the years is long and absurd. Fortunately, in my city, I ultimately found a small 'boutique' specialized practice of former University of Florida Veterinary school faculty. These guys practice vet medicine at as high of a level as most physicians practice human medicine, with internal medicine, ophthalmology, dermatology, oncology specialists etc... It is expensive to do it right - CT scans, body scans and other tests that we don't hesitate to order in people are often beyond the budget of most folks going to "local vets" hence they may dumb down their practice of medicine to folks' budgets. I suspect if you live in or near a major city there might be a well regarded vet school at one of the universities. Go there or ask if they have a relationship with some specialists in your area.
For instance - I'm not sure why your vet is giving your dog vitamin shots. Unheard of in people at least, and I've rarely seen in except in the rare cases of true deficiencies. In addition, in people at least, steroids classically can raise your white blood count. That could account for some of it. At the same time, they weaken one's immune system some so typically should not be used if a serious infection is suspected.
Unless you have a great local vet, I would not mess with them for anything but the most basic stuff like annual heart worm and fecal tests. The few vets I have treated as patients have even told me that the annual vaccines most vets push are total b.s. after the dog is a year or two old, and might even be bad for their health. About $250 a year though.....
