How do I stop feeling jealous

Went to a very large golf tournament and there were thousands of women who were dressed like sluts and very provocatively dressed. Although my man is very respectful and doesn’t stare at the women.. he does a sneaky glance , (like most men ). I know it’s a mans instinct to look at attractive women but god it’s to the point it ruins my time when we are out and makes me uncomfortable and hard to get my mind off of it and be in the moment. I have gained about 60 lbs since we’ve been together and I know I’m projecting my insecurities and negative , irrational thoughts. I hate it. Why do these girls have to walk around like such sluts?!