If you are so sensitive to that, then your SO should know that looking at, commenting on, or flirting with other girls would bring on an emotional allergic reaction in you.

It’s almost like, you two have to go places and him not react to any girls at all, many, many times, for you to be “inoculated”.

He has to praise you in front of other beautiful women.

You have to hear from other people how much he talks about you and loves you.

Maybe you never got praised. Maybe someone chose a pretty blonde over you. But I suspect once you get genuinely celebrated for your own beauty, inside and/or out, and KNOW, truly KNOW that you are loved for YOU, even when you’re eighty, this “thing” will go away.

Then, maybe, one day, he could start a conversation with a gorgeous girl and you won’t feel jealous at all.