help! 3 week old refusing to feed

[PracticallyImperfectInEveryWay]

3 week old and BF, got over thrush about a week ago but now for some reason refusing to feed :(. Goes on for a minute fine, but then purses lips and pulls away but screams when off. Can anyone help please with what might be causing this and any suggestions to fix it? Thank you.

Could it be fast letdown? Kellymom have info on that.

Thanks japhrimel, will go and have a look at kellymom now.