My girl Tess, who will be 11 months in a couple of weeks was one of the worst nippers I ever had. My husband and I were always covered with bites marks and bruises, I had them on my hands, arms, feet, ankles, legs and believe it or not, face. Yep, she even jumped up and bite me on the cheek one day while we were playing due to her over excitement of trying to get the ball away from me. It's hard not to get angry at them but you really need to keep it in check. I use to go in to my bedroom, slam the door and cry. I seriously thought I had an aggressive puppy on my hands. I would try walking her but she never wanted to stray far from her comfort zone, so she would anchor herself to the ground and if I managed to get her to the end of the block, she would turn around and pull me all the way back to her yard.
It wasn't until I hired a behaviorist/trainer to assess the situation and found out that Tess was just being a normal GSD puppy, for the most part, and needed lots of training and exercise. One of the best things I got for Tess was a flirt pole, she loves it and spends lots of time chasing after the little toy I tied to the end of it. Her trainer would also bring over agility equipment and use that to tire her out, it made a huge difference in Tess. Once she had a lot of exercise, I was able to work with her better also. I started out teaching her to heal in my kitchen, baby steps. Graduated to the driveway and today, Tess walks right beside me, which is so nice when your walking a 76 lb dog, trust me. I also send her out on adventures with other dogs, when she was a smaller puppy, she didn't like playing that much with other dogs. I tried daycare but she would stand in the corner and watch all day long, never interacting with the other dogs there. Once I tried sending her out a couple of times a week on adventures with other dogs, she loves it and plays and interacts with lots of different dogs now. She also learned to swim by watching the other dogs.
Today, she is just the best girl, she's loving and gentle, oh she still gets nippy on occasions, especially when she gets excited, but it's nothing major, nothing like she was at 4 months of age. Have faith and good luck, it does get better.
