FTM bottle feeding problem question

pinklilly122

Im a ftm mom to a 2 week old, and have been bottle feeding LO breast milk. We had a lot of issues and Lo was small when he was born so this is just what we decided to, so please no preaching about breast feeding I just need some opinions. We are using Avent bottles with the slowest flow nipple they have. Up until now haven't had to many issues. LO seems to be swallowing air he is very loud and gulps a lot.He seems to be getting more milk then he can swallow because there is always some leaking out the side of his mouth. I burp him a lot and he does not spit up very much. Since last night he seems to be getting upset while eating. He will eat well for a few minutes then suddenly get mad, scream and shake his head back and forth. Ill stop and burp and go back and do it all again. Does this sound like a bottle, nipple issue or something else? Any ideas would be helpful!