open relationships are a bad idea

so, my husband and I have a very different sexual relationship. everyone has their things they are into and my husband happens to be turned on by me having sex with other men. I don't do it often and I don't just sleep with any/everyone. the main guy I sleep with us his brother (I know. awkward.. I thought so too at first). Well, I slept with him last night and for some reason he only lasted 8 minutes.... usually it's 45 to an hour. my husband was pissed that he wasted our evening to come over and last 5 minutes. He said we were done with the other guys, which I'm definitely ok with bc I do it to turn him on more than for me. but because he came home mad I've had the worst guilty feeling all night. I couldn't sleep. I have that feeling like i cheated even though I didn't. I'm just down right sad right now. open relationships are just a bad idea.