Throughout puberty, you might see or feel lumps and other changes in your breasts. During your period, they may even feel a little tender or sore. Most of the changes your breasts will go through are normal. To get used to these normal changes, it is important to regularly do a breast self-examination (BSE). You should do a BSE once a month, about a week after your period starts. Let your doctor know if you find a lump or pain that you are not sure about. But keep in mind that harmless lumps are common in young women. Your doctor can show you exactly how to do a BSE.
Support for your breasts
Having breasts is a normal part of being a woman and you do not have to change your life because of them. If you find that exercise is not as comfortable, try wearing a sports bra with a snug fit for support.
Used with permission: http://gynaecworld.com