Anybody know what could be wrong with my dog?

It could be a virus inside your dog. Or several other viruses! but tending to your dog loosing fur could be from several things such as, food allergies, poor diet, or even..... i would think maggots but that sounds stupid. will walking your dog, your dog may of eatin something poisonous, like a spider, or a bad plant that are not ment to be ate. but this is just guesses. I hope for the best in your dog!!