Various conditions can cause lumps in the breast, with the most concerning being breast cancer, as you mention. A primary care doctor
or obstetrician/gynecologist can perform a breast exam and ask you more questions about these lumps as a first step in evaluation.
The most common cause of a breast lump in a woman younger than 50 years old is a fibroadenoma, which is a benign (non-cancerous) overgrowth of fibrous tissue. Fibroadenomas typically do not cause pain. What you describe sounds more like fibrocystic change, which consists of non-discrete nodules that are often tender. Breast tissue that has undergone fibrocystic change is often more tender around the time of menstruation, and is also benign. Cysts can also be tender at times, particularly if they have become infected, which usually shows up with surrounding redness on the skin. Since you describe that these lumps are near the nipple, it would be possible for them to be ingrown hairs, but it is difficult to determine without performing a physical exam.
I recommend that you see your primary care doctor for a breast exam. It will be helpful if you are able to tell him or her about any family history of breast cancer (relationship, age at the time of diagnosis, any history of genetic testing). If he or she feels further investigation is necessary, the most likely next test would be an ultrasound
, since mammograms are less helpful in younger women who tend to have dense breast tissue.