Please Help

Yes I know I should have ask this on the Advise club I just thought most of anda are on there to so if anda have any advise can anda please answer
My now exboyfriend broke up with me because he had asked my bestfriend if he should go out with some girl named brittney and she told him yes that he should and so he broke up with me cause of my bestfriend and im so hati, tengah-tengah broken what should I do i been with him since 5th grade and now cause my bestfriend we are no longer together how should i deal with my heartbroken and should i still be Friends with her even if she did that to me