I was searching through looking for posts on this and was so happy to find yours! I have been having the same problem. I was just describing it to a lactation consultant and I said the same thing, that the pain wasn't a skin pain, it seemed to come from the inside.
For me, this is lasting almost a week before I get my period. It's making me consider weaning, it feels so awful. I just BF and grit my teeth sometimes. Not good.
So did calcium work for you, MaryTG?