I'm never worried when my missus goes out to town or when I'm at work. I just don't feel that threatened about other guys. She has openly told me about a few occasions when other dudes have attempted to hit on her. I also know most of her male friends, not to keep tabs on them, but 'cos they're all nice guys. There's this one friend of hers, a bit of a big guy. I know it's a nasty stereotype, but the dude looks like a really hc geek, you know what I'm saying? Still, he's nice enough to be a friend of mine. I learned once from my woman that he had attempted to hit on her once. Not too openly, but kinda really craving for attention, doing the whole "I'm a lonely guy and you're my best friend" routine. After telling me this, she asked me if I was jealous. I shrugged my shoulders and asked her if I should. She wouldn't reply, so I just told her it's water under the bridge, no harm no foul. And my woman just hates that about me. She just wants me to be overly protective and a little jealous sometimes. I guess she'd think it to be cute or something.
And the reason I can do this? Act all secure and shit? 'Cos deep down I know two very important things. First, I can always count on the missus to not do anything wrong or stupid (relationship-wise), and second, I could break all of her male friends like twigs if it ever came down to that. Okay, so the big guy might put up a fight, but her friends aren't exactly strong or anything.
So, uhh, I dunno, try weight-lifting or something? The better and healthier your ego, the easier it is to trust others. Also, stop taking things so seriously. It she cheats on you, then that's that. But acting like that can actually be the catalyst for this sorta behaviour. Just chill out and enjoy the love of yer companion while it lasts. I know it sounds really cold but it really isn't.