It is definitely normal for one breast to be larger than the other breast. Most women do not have symmetric breasts and definitely are asymmetric in size or in appearance. Definitely, if this is a change or a new concern, I would advise you to see your primary care physician
or seek referral to a women's health specialist to have a clinical breast examination performed.
will be able to ask relevant questions especially about your own medical and gynecologic history as well as about your family history, mainly to rule out the most concerning disease process of cancer. If at all, an abnormality is detected on exam or on suspicion based on clinical decision, your doctor may even advise you to have additional testing done. It all depends on your clinical situation, and on your personal history. A patient who has a personal or a family history of breast cancer, a new rapidly growing palpable mass or growth is definitely of more concern. In addition, breast size and consistency can also change based on your menstrual cycle and the breast may normally just have a more lumpy feel in younger women. To accurately diagnose and treat your questions, I would advise you to see your physician for a regular breast exam and to learn to perform a self breast examination as well.