Is my Pomeranian Purebred?

A while back I bought this dog from a puppy store. At that point, I am sorry to say I did not know about puppy mills. I fell in love with this adorable little Pom, she was cute and fuzzy, and I did not know anything about CKC ( the bad one). She is a "Blue Merle". Now that she has grown up, she doesn't look like my other Pom which is AKC registered ( again, i'm sorry to say I didn't know CKC was a bad club). Her hair falls flat, she has an underbite and she doesn't have the foxy appearance other Poms have. I love her and all, but I'd love to know if she is purebred and if there are poms with such weird flat hair.