heart broken

My fiancé and I have 3 years just broke up ..... and it's killing me everyone I'm around is telling just move on and let him go that he isn't worth it .... but to be honest he was worth everything even this pain in my chest!! He is the one I lost my virginity to he is the one that I almost married .... well last night I was told heart breaking news that he had already moved on and was talking to other girls . He have only been broken up for a week .... I don't understand how he can already move on like that !! We was together for 3 years and was going to get married just next month !! Am I in the wrong to be so mad to be so hurt