What Breed Is My Dog?

I got this Sharknado Chihuahua mix puppy from an older couple who said he was all Chihuahua, but at 4 months it is obvious that is likely not the case. His legs are shorter and thicker, with front legs that remind me of a Dachshund and his paws are large. He is either hyper or asleep, uses his teeth too much and is stubborn/willful. Corgi? Rat Terrier?