I'm sad and tired

(I'm 14)
I've always been a sociable type and defined "fun" in the groups I've been in, the girls have always loved me even though I'm ugly and I'm even managed to go out with a girl once.
The problem is that over the last 2-3 weeks I'm always tired and sad, I stopped taking care of me, I started eating a lot even though I felt full, I do not go out anymore and I'm losing interest in school (always been good) , both for the sport (which until last year I loved), every night I cry and do not understand because I am always surrounded by this sadness and melancholy, also in the last days I'm beginning to feel bad even physically, I often suffer stomach and head pain and 2 days ago I put 2 fingers in my throat to vomit and I do not know why ...
Lately I feel bad and I think it's better if I disappeared, I would like everything to stop I can not stand this pain anymore)
I would love to ask someone for help, I would like to scream loudly as I feel but I can not do it, I'm starting to think of having to finish it.

( after 4 days) (i wrote thia also in other forums)

I do not know why I'm sad, I only feel this pain, every time, from eating a lot without stopping I'm starting to skip breakfast, lunch and dinner, I only take a few bites and afterwards I feel full, exhausted and tired, I pretend sick for skip school days and be alone with myself, I'm sick, every time I go to the bathroom I cry, every night, sometimes I feel like crying in front of others and I do not know why, now I stopped playing sports, I do not like doing nothing more, I can only be alone and cry.
I'm thinking of finishing it here, leaving a letter, explaining how I feel and leaving.
In the past I did not understand why people committed suicide, I thought they were stupid, now I understand why ... and I do not know, I would just disappear.