4 month old baby loss of appetite and throwing up

my LO is 4 months and have always been good woth his milk and even got to have 8oz every 4hrs. 

This last week, however, he has been playing uP. Has 4-5oz then wont take anymore. I burp him and try and feed him the rest. Sometimes he has it n sometimes he doesnt, but its a constant fight. He has also been spitting up alot of milk after every feed, sometimes immediately after, and sometimes later. 

Oddly though, this past week he has started to sleep through the night. I think he might be teething, but does this happen? 

Any advice or if people have gone through this before?