Am I Depressed?

I think I may be depressed. I am always tired, I never have any enthusiasm for anything, I have gotten really lazy, I’ve gained lots of weight, and my social life has gone down the tubes. I also have become somewhat anti-social, because I always just want to stay home and watch movies. I don’t even interact with my mum and sister as much anymore. It dosen’t seem like something I can just turn off. I can’t just “be happy”, because its not how I feel. I think the reason I may be depressed is because I’m 16 and I’m surrounded by people my age going to parties, and having boyfriends, and basically just having a lot of fun. I feel like my life has no point, nothing ever happens, and as of right now I have no true, good friends. Its new years and I couldn’t even muster up the enthusiasm to smile when my family hugged me and yelled “happy new years!” and fired off some fireworks. What should I do and do you think I am depressed? Because it sure feels like it..