Personally I do not believe Jealousy exists. Jealousy is only Fear and Ignorance competing for space in your brain.
What will I do if he/she leaves me?
It will hurt so bad if I lose him/her.
I don't want to lose everything we have worked for so long.
I don't want my trust to be broken.
Does he/she love still love?
Does he/she love her/him more tham me?
What will happen to our children?
Does he/she still trust me?
Simple, honest Communication is the only way to deal with Fear and Ignorance in a relationship. Tell each other your fears, ask the hard questions, don't expect easy answers, be prepared for change. Change is always a bit scary but change is also the only constant in this world.