Kaz, it could be that his attachment is not so good now that he is bigger and moving around. Sometimes mums find it helps to make sure they are still really close to mum while feeding so that the chin is well on the breast.

The other thing is that pain that is there between feeds as well but worse during them can be a sign of thrush. It might be an idea to have this checked by a doctor if the pain doesn't ease within 24 hours or so. Make sure that if that is what is, that the doctor treats both your nipples and your DS's mouth, or you can cross infect each other.

All the best hun, I hope it gets better quickly.