Why do i feel so depressed and sad?

One Question, which is so killing is Why do i feel so depressed and sad?
Firstly I a boy and high school student. I have a great life, i am a good student, get great marks, have awesome supportive friends, and not family is good enough. But whenever i am around friends i never feel happy or very excited to be around. I dont know why but, i talk to them a bit. but most of the times don't even talk to them even if they r there. i don't feel like or something or i just don't talk idk why. I was fine before but i always feel lonely and all by myself. i like a girl also, but never had luck with anyone. what should i do to feel better, be better, anbd not be lonely. people tell me to be myself, but idk what i should do by being myself. My life is screwed up. i was fine, before but i just am depressed, idk how to explain. what should i do please help ?????

I guess i am too stressed but my exams are over, grade 11 now, one of the main things is why don't i feel like talking to anyone even the one i like?? i never even get a topic to talk about, please help?? i would love to get some good responses, :(

Nowadays i dont find interested in doing anything, even playing, gyming anything is boring, everything i do is like, i have to do it so i should do it, why????????? HElp please, what should i do to feel better or recover,??? i am physically fine, no disease,