Don't know what to do

This is my first an possibly only post on reddit. Basically im just here to ask how I can improve certain aspects of my mental health. I am a high school student who doesn't really have anything to complain about. Supportive family, great girlfriend and friends, good neighborhood, good school but for some reason I have little to no self confidence or motivation. I can't keep myself in the gym and I can't commit to practicing my hobbies. I have a total lack of drive in most aspects in life and feel as if im not really good at anything and nothing is fulfilling at the moment. This has been going on for as long as I remember. My close friends who try to help all say the same thing but it never helps. If anyone knows something I could do to make a change pleas let me know.