I have a tender and bigger breast, and i am not pregnant. what is the cause?

May be hormonal: If you had menstrual cycle during which ovulation did not occur, progesterone is not produced and unopposed estrogen can cause breast tenderness and swelling. This is more common in women past the age of 35 leading to irregular and skipped menstrual periods. Tenderness throughout the breasts is almost always due to estrogen dominance.