My dog has been acting out ever since my boyfriend started spending more time at my house and sleeping over. He's making a mess of my yard, nips at whatever limb he can, and is whining a lot. I'm getting really frustrated. My dog is still a puppy, so obviously he's still learning how to behave. But I don't know how to get him to stop these behaviors, especially the biting. I hate using physical force, but at one point I got so mad I snapped him on the nose - it made me cry, I felt so bad. At the same time I know he needs to be better behaved. What do I do??