It was with my ex who to this day remains my best friend and is now (not at the time) the father of my daughter, and it just kind of happened...my boyfriend at the time was across the country, my ex had just gotten back from a deployment and I was worried about him so I spent a couple of nights just sleeping with him before we actually did anything. We've always had that kind of a friendship though. I felt guilty, but I didn't regret it. And there was no need to confess because we broke up shortly after.