confused..need answers

so i wasn't sure if i had a minor depression or anything..after reading an article in a magazine it hit me that maybe i did. I have been feeling really low for awhile and nothing really triggered it. I stopped hanging out with my friends and got really stressed out a lot over homework and studying. I would study for 4 hours just for a quiz because i needed to get a 100. I always wanted to be perfect because thats what people expect from me. My depression has died down a little and i don't cut myself as much..maybe only once a week sometimes even for no reason. I am 17...5'3 and weigh about [edit] pounds. I was born a twin and was always really small...anyway..just recently for maybe a month i have been feeling that i am fat. everyone always says to me though that i am so skinny..still weighing [edit] pounds...but i really lost confidence and feel as if i needed to be thinner. within a 2 days i would lose weight and go from [edit] pounds. I would weigh myself at least six times a day and get really upset if my mom was buying to much food at the supermarket..to the point where i begin to cry. I still eat everyday..just less then what i used too. I have a big family too so meals are large and always everyday. i would wake up early and tell my mom i ate breakfast when i didn't and hold out until dinner. other times i do eat breakfast and dinner too. I feel guilty tho after because i know i am eating and gaining weight. I would say "can i take a shower" and run the water and the radio and try to throw up. a lot of times it would never work and i would start crying because it never did. I would google "how to make your self throw up." even seeing the harmful things it can do to you didn't bother me. I constantly look i the mirror to and still see myself as fat when i know i am only [edit] pounds. but i feel like being thin is expected because i've always been that way. i'm also really sensitive where my dad would be like.."watch your figure" if I'm snacking..i know he jokes but it really got to me and now i don't ever snack anymore. I don't know if this is considered bulimia because of the fact i TRY TO throw up and eat less. sometimes i do throw up but it's rare that it works so then i resort to eating less to make up for not throwing anything up...sometimes i cut myself too because i just get so angry unfortunately..it makes me feel better for not being able to be the way i want to be or throwing up. I am constantly measuring my wrist. Also, my mom always wants to go out and eat and stuff and takes me..i don't want her to know i am struggling but i just hate eating..i feel gross after i do. I go to bed hungry a lot too and get excited to go to sleep because i know when you sleep u loose weight. I don't know what to consider this. school is starting now too and i am scared with lunch and stuff because I'm not going to want to eat it but people will notice if i don't. Am i bulimic? anorexic? or just depressed? or none? help. I need advice.