Re: Baby latches fine but....
May guess is that your little guy just needs to learn that in order to get fed, he needs to keep sucking. It sounds like he wants your breast to work like a bottle- that is, to reward him with food even without him needing to put in much effort. My thought is that the more you can hang in there through the latch/unlatch cycle, and the longer you can go before using a bottle, the more he'll learn that nursing takes effort and effort produces reward. You also might want to try using breast compressions to keep the flow going.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"