Hi! I believe I can be of help with this issue.
First, let me say I can imagine how confusing and distressing this situation must be for you. These fears are very long term. Having kids was able to distract you from them, but it didn't change the fundamental dynamics in your emotional self. And so it is now back, and it sounds like the jealousy is back with a vengeance.
At the heart of your jealousy is a worry about your own self-worth. She might decide you are not worth being faithful to. What if she decides she wants somebody else instead of you?
You may wish to spend a brief time in psychotherapy exploring your jealousy: the fears and lack of self worth. This could be very useful and important. But you might want to first try using some self help books to help you. So let me recommend some that I think are among the best and that are readily available in libraries, stores, and online:
If This is Love, Why Do I Feel So Insecure? by Hindy, Schwarz, and Brodsky. They discuss their idea about "anxious romantic attachment" which is how they describe insecurity in relationships.
Life Without Jealousy: A Practical Guide. by Lynda Bevan. Good exercises here.
The Courage to Trust by Cynthia Wall. Gives a good understanding about what in your personality is involved in this dynamic of not being able to trust.
Okay, I wish you the very best!
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