Why did he brake my heart?

i am not suposed to be dating untill i am sixteen, and i am15 now but he said he would wait for me. he is a very kind person, he always puts others befor himself and he loves helping people with there problems he is a perfect little church boy he hates hurting people but yesterday i hung out with him and he acted the same way. he told me tht he loved me, est. but today i got on facebook and i found out he is dating another girl for a week. i dont kno wht to do, i feel crushed...like someone tore my heart out....what should i do? and why did he do that to me?