Maybe someone could help me out here...My german shepherd puppy just turned 5 months old. She lives with me and my boyfriend and was fine until about a month ago. We were at the dog park and this lady walked past to get her dog, and my pup jumped up and nipped her hand.she was okay, but it took me off guard, because she had never shown aggressivness before. when my boyfriend was alone with her, him and even his cousin would play with her in the yard & she was fine and really liked them just as well as she did me. In the past few weeks, whenever im around my boyfriend, she wont come near him and growls, but alone with him she was fine? Yesterday night, he let her out to use the bathroom. He was trying to get her back into the house ( which really doesnt enjoy and runs because she LOVES being outside ) so he was calling her name with no avail so he went to pick her up ( like he usually does ) and out of nowhere grabbed onto his wrist and arm and wouldnt let go, needless to say she hurt his hand and arm.We've taken her to obedience school and in public almost every single day to socialize her .I have owned many dogs, from chihuahuas to border collies to pitbulls, and they've never suddenly did a 360 like this, so im not sure what to do? I LOVE my dog, she is extrememly loving and loyal, but im so worried.shes UTD on all her shots and just got back from the vet at the beginning of Feb and everything was in great condition! PLEASE and advice or personal experiences would be so helpful!