What do i do when im in love with my ex. and has a girlfriend and i all ready have a boyfriend?

well me and my ex were together for 3 years. he was my first for everything i mest up our relationship with being a flirt and lieing. But he was a Very Jelouse. The only bad thing about ous is we both love to be in charge of the relationship and thats what made the relationship fall. All my friends tell me not to get back with him .Right now he has a girlfriend and i have my boyfriend. but i cant help felling so much for him and it hurts me alot what do you think i should do??????/ i dnt want to mess up anything HELP