“I am developing breasts, am I becoming a girl or a transgender?”
It is to be noted that both boys and girls possess both male hormones (androgen) and female hormones (estrogen), except the fact in boys, the androgen dominate and in girls, the estrogen dominate. Both these hormones start secreting in the body at the onset of puberty and the body takes some time to sort the levels of respective hormones. Meanwhile, it is noted that the boys have develop a very small tissue around their nipples, which looks like a breast. You can be very sure that they do not grow more than that, but the hanging tissue around the nipples may take some time to settle down. Mostly it will settle down around the age of 20 years, when puberty gets over.
However, even after the teenage, the condition does not get settled, it is necessary to look out for them. The imbalance of estrogen and testosterone might not have sorted down and this condition is referred to as Gynecomastia. Though it is not a very serious problem, men with breasts might feel little embarrassed with it. Wearing a loose fitting dress might help in the condition to be less noticeable.
If you are not comfortable with it or you observe some symptoms like pain, tenderness or swelling in the nipples, it is better to approach a doctor to identify the issue and solve them. It is also to be noted that substance use and drugs can be root cause for Gynecomastia. The doctor might suggest taking a hormone balancing oral medications or rarely might suggest surgical method to remove the breast tissue.