Is it normal to have lopsided breasts and saggy breasts during puberty? Will this change?

Most women have asymmetry but the degree it varies from patient to patient.  Depending on your age, puberty development, and severity, you may or may not be a candidate for intervention at this time.  Make an appointment with a PS to get evaluated and counseled appropriately based on a more thorough history and physical exam to learn about your options and when the right time is to intervene. 

Thank you for your email. Without examining you, or at least seeing a photograph, it is difficult to give you any specific information relative to your particular situation, but from what you describe, it is not  uncommon for adolescent girls to have some asymmetry and some sagging. Your breast shape is entirely dependent on genetics and luck. Some women are fortunate enough to have pretty and relatively symmetrical breasts, and others might be less happy with their breast appearance. Most adolescents and women will find that their breast development is complete by around age 18, but many things can affect breast shape over a lifetime including weight fluctuations, skin quality, hormones, pregnancy, etc. If you are concerned about your breast shape and you are a minor, you should discuss this with your parents and try to schedule a consultation with a board certified plastic surgeon. Most plastic surgeons would be qualified to make the proper assessment and recommendations for you as to your treatment options. In general, it is almost always the case that we can achieve a significant improvement in breast shape, size, or both for the adolescent or woman who is unhappy with her breasts. Best of luck to you, and remember, you are not alone. 

If your breasts are uneven and bother you, I suggest you go to a Board Certified Plastic Surgeon for an evaluation.  I do not know your age, the shape of the chest wall and breast or the quality of your skin.  Congenital breast deformities are common and sometimes overlooked and not recognized.  One breast may not develop fully. The breast shape is sometimes described as tuberous with lack of the lower half of the breast.

Most often we think of breast droop caused by weight loss, or breast feeding, however it is true that for some the breast will develop with the nipple a bit lower than we would like and have a droopy appearance. Asymmetry is also fairly common, more so than many appreciate. Things may change for the better as you grow and develop, though currently you are very normal. the bra at night is just fine, no harm in that, and a well chosen bra will help you look your best during the day.