The breast tenderness could be from the change in your hormones. Since it is the same on both sides, it is not likely to be cancer. Checking with the doctor is a good idea because he might be able to adjust the dosage of your medicines or tell you how long this symptom lasts. Women who have gone through natural menopause who extend their exposure to estrogen through hormone replacement therapy do increase their risk for breast cancer. You don't mention how old you are. If you are much younger than typical menopause, you are replacing the estrogen your body would make naturally, not increasing it. As long as your doctor knows about all the estrogen products you are using, it should be fine. Don't add any drug store supplements without discussing them with your doctor because many of them contain plant estrogens.