Sign up for the Slatest to get the most insightful analysis, criticism, and advice out there, delivered to your inbox daily. How to Do It is Slate’s sex advice column. Have a question? Send it to Jessica and Rich here. It’s anonymous! Dear How to Do It, I came home early from work to find my husband (we’re both men) in bed with three other guys. We sometimes bring in a third party, but it’s always...