Training a Puppy Not to Bite?

I've had my Shar pei/Pitbull puppy since he was 8 weeks old and from then on I stressed how important it was to not let him bite. My fiancee and I went out and got him ropes and treats because he was starting to bite. He is 14 weeks now and he is starting to draw blood and bite harder and bark at our hands.

My mom's friend came over and was rough housing with him and letting him bite and bark. I'm afraid I'm going to have to get rid of him. He was a wonderful when he was younger and was good. Now he doesn't listen, he barks, he bites, and he is scratching now. I've tried saying no sternly, avoiding him til he behaved, put him in his kennel til he settled down, and my mom doesn't know what to do so she grabs his jaw spanks him and says no biting.

I love my puppy, but this biting thing may lead me to giving him up or my mom just taking him to the pound. My fiancee wants to get him a muzzle and I want to be able to trust my puppy especially because I may be pregnant and I have a 6 year old nephew. I need to know how to get him to be good and stop biting.

By Samantha B.