What are other reasons for breasts to hurt and feel swollen aside from period, pregnancy or pms?

Breast pain: There are a number of factors which can cause breast pain and the feeling of swollen breasts. These include pregnancy, hormonal changes, sometimes birth control pills, excess caffeine ingestion, and a condition known as hyperprolactinemia (which often results in production of breast milk during a time when there should not be any). It is helpful to see your physician for these symptoms.