Its only best to pretend your not,lol. There's nothing you can do not to get jealous.Think about the things you and your ex useto do together,think about how much both love had grown after a short peroid of time and tell your self that this other person can not make your ex falls the way he/she did for you and think about how they don't do the things you and your ex use to do....at the end of the day you win because u have already had that heart,capture that heart which still loves you un-conditionally :)
'Don't hate yourself for feeling jealous when your ex has another person in his/her life,be proud you have had that person before to look back at now and feel free to let go'
Queserra