I was in your exact position a few weeks ago with Lexie and things seemed hopeless. People suggested the yelping method which i tried to no avail. I think some pups respond to it and others don't. When i yelped at Lexie she would get this excited look on her face and lunge at me with mouth open, i'm pretty sure she thought it was a game
. I also tried holding her on her side, the "showing dominance" technique and that made her very aggressive, and as soon as i'd release her she'd be back trying to nip me and bit me many times very hard, my hands looked like i'd been playing with broken glass it was bad. What worked for me was the spray bottle with water and time outs. Every time she niped me i'd spray her with water and say ah ah!, if she did it again i'd pick her up and hold her in front of my face, make eye contact and say "ah ah!, NO", and immediately place her in her pen and walk away, 15-30 secs later i'd take her out. The reason i added the spray bottle is because Lexie didn't get that "no" meant she was doing something bad and needed to stop, the word "no" had no power or meaning. Now i don't even need the spray bottle i can just say no or ah ah and she will stop immediately, she never bites me hard anymore just very light nibbles, because she now knows bite inhibition. It took some trial and error to find what worked for me but i'm amazed at how much Lexie has improved