I think I'm depressed but no one seems to notice?

It's really hard for me to reach out and ask this but I don't know what to do anymore. I'm 15 and for the past 2 months everything in my life has gone downhill.I feel so hopeless all the time. I can barely eat and i can't sleep anymore. Nothing I used to do seems worth doing anymore. Often I just sit in my room and cry which makes me feel weak. The problem is I don't know how to change. My parents don't notice anything and I'm scared to tell them. I've tried hinting my feelings to my friends but they brush it aside like it's nothing. Am I just overacting or should I get help? Please help. I don't want to feel like this anymore.