My Dog whines when he scratches his ears. and he also bites his fur off on his back ?

My dog whines when he scratches his ears, and they look very dry in the inside of them like theres ear wax building up. I think he seems to smell from it or its just his fur, i even gave him a bath and the smell came back the next day. He also bites his fur off on his back a lot and then constantly wants me to scratch him and then whines if i don't. If i pet him you can feel little patches of scabs on his back or underneath his neck. So i was just wondering if my dog either has some kind of an ear infection or it could be ear mites, and also if he has cancer, or a skin disease. And what should i do about it.
Thanks! ♥morgan

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