I think I've lost him😩😭

I broke up with my ex 2 months ago, and immediately regretted it.. but I told him to move on, when I wasn't even moving on😔 and he tried to move on then I tell him i want to be back with him and I POUR my heart out to him, but he can't chose bc he likes one of my ex best friends..😭 I really miss him and I'm in love with him no matter how much I try to hide it I am.. And Idk what to do. he says he wants to be single but all he does is flirt with her at school.. any advice on how to win him back?😕