My 3 month old DD has never refused the breast. She doesn't have reflux or tongue tie.
She fed perfectly well overnight and up to about 9.30am. Good powerful feeds of 10-20 min taking both sides and sometimes asking for 3rd.
Recently she has been chewing her fingers a lot (start of teeth under gums?) and has had a blocked up nose.
Tried to feed her as usual at 11.15am. She was fine until my let down then started to cry and pull off. I thought maybe the let down had startled her so waited and tried again. She started to suck for a few seconds (bearing in mind this was after let down so milk was there but not forceful) and then cried and pulled off, almost like a sore mouth?
She has been like that ever since. Asks for food (though not starving hungry) then screams and cries after a few mouthfuls. She gets annoyed and won't drink. Perfectly happy when sitting or playing and not feeding.
She can suck her/my finger OK.
Rang the NCT who suggested using a feeding syringe if I was concerned but to ask here and keep trying in the meantime as it might well settle down.
Any ideas? Teething? Sore mouth/ear? ...its happened literally 2 hours after a perfectly happy feed! 
I'm shedding hair post pregnancy and worried one has got in her mouth or something and hurt it 
but I think this is just random anxiety. I checked her mouth: it looks normal.
Any tips as I don't want her to get starving hungry or not feed so long it affects supply. Thanks!