I get erections when I sag?

I love to sag my pants and show off my designer boxer briefs to the world. The one slight problem is my sagging makes me incredibly horny and I can't help getting boners which make a tent in the front of my boxers. Like Yesterday I was on the subway with my girlfriend and watching my sag in the train window gave me a ***** which showed. At one point my girlfriend whispered to me: 'Looks like your big boy's come out to play again Sam' causing me to get even harder. Do any other guys get horny when they sag?