Introducing my Pit Bull to a new dog?

[DiPsEy DoO]

Hello! I have a 2 year old APBT. He is one of the most well behaved dogs I have ever had the pleasure of owning. He has many friends that are dogs. Here recently, he has been aggressive with other dogs. It is mostly over me. I took him to a friend's house to play with her Pit Bull. They got along really well. She began chewing on a bone. He wanted the bone. He waited patiently by the bone until she walked away from it. Another friend brought her dog over who is known to be aggressive with toys and bones so I decided to take the bone away. When I picked it up, the other dog came to me begging for the bone. My dog attacked her. He never actually bit her. Just pinned her down snarling. 2 months go by with no incidents. I went camping and took him. I let him run off leash and he was really good the first night. The second day, another guy brought his dog. They sniffed and then started playing. Around dinnertime the new dog came up to me and started harassing me trying to get the steak I was eating. My dog knows not to beg so he was laying down about ten feet away. When he saw this dog try to jump on me to get my steak again, he attacked. I have been really paranoid to bring him around dogs ever since. I recently started dating this guy. He has a dog. We've taken the dogs to the park and they've sniffed and walked together just fine but I've been afraid to let them play. Will it ever be possible for him to get along with a new dog? How should we go about introducing them in such a way that they can play? He loves to play with his existing dogs friends. When I take him over to his apartment, we keep them separated. One on the balcony while the other is inside and we switch them off. They just sit at the window wagging and staring at each other. How can I fix this? I know it will be completely naive of me to assume my dog is going to love every dog he meets.

 

[Bumblebee]

It doesn't sound like dog aggression. He's being protective of his female (you). Think of it as something like food guarding, but you instead.

Practice control techniques by having him maintain a stay while you play with other dogs. Remember 3 things.
1: Make sure he can't get to the other dog.
2: Give him something fun to do.
3: When you're with multiple dogs you should treat all of them equally.

He should be waiting for you to handle situations and never take the initiative. Practice other 'Learn to Earn' techniques as well.

While you're getting the dogs acquainted and building your trust in them you can keep them separated inside your apartments. When you have play sessions take them to neutral locations.