Patricia ,

Could be any of your listed possibilities but, I'd vote for the likelihood
that the baby is developing a rate flow preference. Has mom tried stimulating
a m-e-r just prior to and during feeding to increase availability and flow?
ie; relaxation techniques, imagery, nipple stim, breast effluerage. Re:
soreness; Is baby chewing or pulling to stimulate m-e-r and faster flow?

Deb
Springfield,VA