I Breastfeed My Baby And After Feeding From The Right

I breastfeed my baby and after feeding from the right breast, I often get an intense pain throughout the breast that varies on intensity and duration. It lasts between 1 and 3 hours at a time and has been painful enough on 4 different occasions to make me cry out loud. This has been happening for roughly 4 or 5 months now. Compresses, massages and pumping let down does not assist with the pain. It is not cracked nipples, engorgement, clogged ducts, mastitis, a yeast infection or an external bacteria issue. A mammogram scan came up clean. What else could this be?