help.. its important:( :( :( I need answers soon before i go crazy?

Well in 7th grade i had a really hard year i had no real trust worthy friends and my grandma died a few weeks before i moved, oh yeah i moved away from all my real friends. So for that year i was insainly depressed and thought i just wanted to disappear, and it keeps reocuring. In 8th grade I became top of the school but still got this really low lows when everything was great and i got way too high of highs where i thought i was perfect and could do anything, then the next week i would want to die because i thought i was fat and ugly when i am 14 and weigh 85 pounds. Im shortish 5'2 so im not like a stick but not at all chubby. I am writing this because for a few months i feel normal then after i feel like depressed then a month goes by no probs and i am insainly happy. My aunt has bipolar and i have a twin but she is nothing like this. I feel like this is not normal if it is i cant take it anymore. I have never attempted suicide because i love my family but what do i do? Am i depressed, or bipolar or do i have an image disorder.