I never had a full on 3-some. When I was in high school, my friends (a guy and a girl) were together and the 3 of us messed around. I don't think I could ever have a 3-some in a relationship because I wouldn't want to see my boyfriend with another woman, and I wouldn't want to be with anyone else. That's my stance on it, in my current relationship. In the past I was open to it, but not while I was in a relationship. I was always too afraid of what it would do to the relationship. I'd say definitely do some thinking about it and make sure you want to see him with another woman before you bring it up to your boyfriend.