Hey, I didn't want to read and run, but I havent got a real answer for you, but Niamh used to do this, it is really painfull! I know she grew out of it eventually, don't remember how old she was (I bf her to 9 months) I think she did it much less when I fed her laying down on the bed with her, give that a try and see how it goes.
Sorry I couldn't be more help xx