It seems like I get jealous when I hear suggestions that females I'm interested in AND know personally might be banging other guys.

eg. I used to pick up on hints that an FWB that I had was going for drinks, etc with other guys. Somehow that annoyed me and made me feel jealous. But I know I have no right to be and have absolutely no idea whether she even went for drinks or is just seeing friends or whatever.

Generally:
This seems to be a constant, jealous streak which I can recognise but haven't been able to fully shake off.

Aside from casting my net wider, what can I do to help get rid of it? If I was in a relationship, surely this behaviour would be magnified unless I really really trusted her...

The FWB relationship only works if you both want it. Either fuck other girls or if you cant handle your own insecurity / jealousy problem, break up with this one and get a proper girlfriend.

If she is fucking other guys she is doing nothing wrong because you two are not a couple. If this is the girl you want, suggest she becomes your girlfriend. If she turns you down, keep her as a backup when you need sex during dry spells and fuck other women.

I experience something similar but for different reasons, which I will go into when I make my own thread about it. Recognize that this comes from a deep-rooted gender dimension where the guy finds normal to see multiple women, but expects the woman to only stick to him. Its tied with evolutionary behavior and it takes a lot of work to get over, but worth investing time in doing so. This is to me one of the biggest examples of Mystery talking about how our minds are outdated machines that havent evolved to today's world. It would be normal not to care right because she isnt your girlfriend, yet you do anyways.

It's probably because you don't fuck other girls. If you hooked up with other girls besides her, you wouldn't feel bad that she does it.

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