Threesome

My boyfriend and I constantly talk (mostly joke? To me at least it's more like joking/teasing) about finding a chick to have a threesome with. But when I actually think about it seriously it makes me nervous but also turned on at the same time. I'm worried it would affect us (me) and I would think that he enjoyed sex more with her. What do you guys think? Has anyone had a successful or unsuccessful threesome experience? Need opinions!