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What it sounds like Stewie may be experiencing is what is called a pyoderma or a skin infection. These can cause bumps as you describe as well as itch or sensitivity to touch. They are often secondary to underlying allergies in dogs which also can make his skin uncomfortable. Dogs can be allergic to various things including environmental allergens, food ingredients and fleas. In young dogs especially, we also have to be concerned with the possibility of mange mites that live in the hair follicles being an underlying factor.What he needs is an exam by your veterinarian so that these things can be ruled out and the proper medicine may be prescribed. If there is an infection, he will need at least 3 weeks of an oral antibiotic. Many of these dogs will also need a short course of steroid to break the itch cycle in some cases. In cases where the sores are widespread as you describe, topical treatments are not usually effective and oral antibiotics are needed.
In the meantime, there are a few things that may help and certainly won't hurt. An antiseptic shampoo from the pet store can decrease the bacteria and yeast if they are present. I like the product called Hexedene® because it contains chlorhexidine which is effective on bacteria and yeast. There is also a "leave-on" product called Resi-chlor® with similar ingredients that can be used on the lesions themselves.
I hope this is helpful. Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please reply so I can clarify for you.