Why did she leave me...?

weve known each other since kindergarden (now we're 16) and we've been going out since beginning of december we go to the same school and in summer we see each other a lot. she visits me, i visit her, i take her out to dinner, we walk on the beach, its a perfect relationship and its the first time ive been in love with someone. not only was she my girlfriend but she was also my best friend, we told each other everything that happened in out day and we trust each other with our lives. last night we went out to eat with a few friends and then i went over to her house. then today i got a call from her and she was crying and i was worried and asked her what was wrong, she said "i think we should break up" i didnt say anything, i was shocked and couldnt believe what she was saying and couldnt understand why.. i said "wait..what?" and she just said we should and asked hung up before i knew it i started crying..icalled her back and she wouldnt answer so i went over to her house and nobody would answer the door.. theres no way i can contact her..why would she do this to me? and with no reason whats so ever? we trust each other more than anybody else i would never cheat on her and i know she hasnt cheated on me..she knows i would do that to her and i havent done anything wrong to get this...somebody please help me what can i do ive never in my life have ever loved anybody this much and ive never felt so heart broken... im crushed i feel like the world would end i swear...someone please help me i really need help with what to do..