I am having the exact same problem with DS2 at the moment. Except he's not hard to settle after a feed. I am also expressing before feeding, which is helping to some degree, but as soon as another let down comes he's pulling off screaming & refusing to go back on. Unfortunately I don't know how to fix it so I can't help but I can sympathise. My MCHN says it's just a phase and he'll come round. She said it will probably take 3 to 4 weeks. I hope that's true for both of us.