Welcome to the forum! Here you will find sympathetic and understanding brothers with similar physical problems.
I respectfully disagree with your prior doctors. Once gyne is established in your early teens, if it doesn't spontaneously disappear within about two years or so, then more than likely it will remain. Many docs point to the magical age of 18, at which time you can vote, drive a car, join the military and your gyne will totally disappear. Unfortunately, the gyne tends to remain -- and it will not disappear when you reach the next magical age of 21, when you will be able to drink legally in most states.
Suggest you have a really good sit-down talk with your parents and then, together, seek the opinion of a gyne specialist in your area.
And feel free to pose questions on this site.
Dr Jacobs