Hi there,
While on Birth control patch few women may experience breast discomfort, breast pain and enlargement of the breasts. This patch contains approximately 60 percent more estrogen compared to other hormonal contraceptive. Estrogen causes some of the glands in the breast tissue to swell .Birth control patch causes consistent release of estrogen which causes elevated estrogen levels throughout the body making the breasts become larger. If you are too concerned it will be best to discuss it with your gynecologist. I hope it helps.
Best luck and regards!