Why I feel jealous and how can I overcome it?

I get jealous if there's another beautiful woman in the same room with my man. I don't know why. I just feel like something burning inside me as if he would not find me pretty anymore. (although that could not be true) I don't say anything or start a fight. I just keep it inside. But I don't want to feel that way anymore. How can I overcome it? It really makes me sad and makes my trust issues worse..
Why I feel jealous and how can I overcome it?
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