Transgenderism and Feelings of Identity

There is the view that ones gender is whatever you feel. I've heard this view in my schools philosophy club, and you can see it in the popular media here. But the criteria that gender is whatever you feel is too vague. Of course, those LGBT advocates want to say that if you feel like a boy or if you feel like a girl then that is your gender (or any other sort of gender according to these people, since according to them it's like infinite). But what kind of feeling is the feeling of "boy" or "girl"? We know there are feelings like anger, happiness, pain, anxiety, and boredom. But they don't say "My gender is boredom because I feel bored." (Well, I have heard one of their advocates say that being a rock is a gender, so maybe I shouldn't put this pass them, but I think a more serious advocate would say that's not possible) No, the type of feeling one has as being a boy or girl is a different kind of feeling as being angry. But the definition of gender being whatever one feels like is too broad to allow for that distinction, so the definition needs to be more precise.