Please Heeelllpppp! i need help asap!?

Why do i feel like somethinq is missing i did have a brother that died , idk whats wrong with me im happy at school sad at home so sad all i do is jam to music and lock myself in my room. It's hard for me to concentrate latley and i have bad mei meory idk what's wrong with me please you quys help i feel like im not goin to be successful in life and i put myself down a lot , i also feel like im not good enough and like i need some big change whats wrong with me??? ://