Hi Anjia,
I have had same on Hrt but coming to the end of first 3 months seems to have eased off.
Also, evening primrose oil capsules used to give me terribly painful,swollen breasts. It got to a stage that it stimulated production of prolactin in me and I was lactating. As soon as I stopped evening primrose oil within less than a week it all went away.
Suz