It will be good to get your son to be evaluated by a psychiatrist who is experienced in evaluating and treating people with gender identity issues. Many teenagers have these kinds of concerns and it is pertinent to see if these feelings will persist. These individuals may be binary trans (man or woman), gender fluid (a person's gender changes over time or depending on his/her emotions or situation), or non-binary (where he/she is somewhere between masculine and feminine). Many people have doubts about their gender or gender expression(even cisgender people).
You can support him by allowing him to talk more about his concerns and getting him the professional help that he needs. Many guys with transgender issues have anxieties regarding their relationship, national service, educational and occupational opportunities. They do need all the assistance that they can get.
