Ok. This is SO strange for me because you have highlighted something I really identify and I've come to a conclusion recently and so...stay with me here.
This very well may not apply to you, so I apologize if I've misread what you're saying.
I felt this same way for a while. Like, wildly uncomfortable at other women being hotter and more comfortable with their bodies etc. As if it was about me being in competition. I'm super curvy, so in some clothing I feel great, but in a swimsuit...way too much curve when I compare myself to other women. And what I'm realizing for ME (maybe not for you, but consider this...) is that this is about me actually being uncomfortable with nudity/sexuality.
I was a Women's Studies minor, and I'm all about body positivity and women having full agency of their bodies. In THEORY. I'm realizing I may be a bit more conservative than I originally thought, because for me my discomfort comes from how I feel about the nudity - not how my partner might feel while standing next to me. I was projecting my own discomfort and insecurities. But I feel equally uncomfortable around naked men and naked women, so this may be different than what you're saying.
If you hypothetically went to a nudist beach with men would you feel the same anxiety? This may help you know if it's a jealousy question, or a nudity question.
Regarding your final 3 paragraphs: assuming monogamy, any partner should make you feel safe in that they will not stray. I know you feel like you'll carry PTSD with you in your future Rs, but I don't think you will. Not if you process it in a healthy way now. So just remember that you'll be at that trusting place again. And you and your partner can walk by all the stupidly hot people in the world and not even bat an eyelash.
