I'd be very interested in hearing what your doctor has to say about this. Like other moms who answered, I think Sadie may have some congestion and/or a possible sinus infection. My other thought is that she's getting far more active and is basically losing patience with either sitting still for meals or positioning herself for breastfeeding for any length of time, causing her to scream out. I both breast fed and gave bottles to my children. My husband and I decided together that we'd have our children off breast and bottles by their first birthdays. With most of our kids, it seemed as though the transition was rather natural at about that time, give or take a few weeks.
Love your sweet daughter through it and be sure to watch for other signs when she acts as though she's in pain. She may play with her ears, pull at her hair, or shake her head.
All the best to you! Please let us know the outcome!
D.