Hi,
What you have is not breast cancer,but a benign condition called
Gynecomastia,like your doctor said.This is caused by an imbalance of the hormones estrogen and testosterone,which promotes tissue growth in one or both breasts.
Generally, gynecomastia isn't a serious problem,mostly it's due to hormones,but it could also happen if men are using illicit drugs ,like steroids, marijuana, alcohol etc...