LadyJane, Intuition is right (she is always spot-on in my opinion
). Your husband is beginning to question himself and his ability to satisfy you. "Why do you want to swing so bad? Aren't I enough?" It's normal. Even those that do swing have issues that arise from time to time.
One big thing swinging has done for us is open-up the lines of communication. The other is give us more faith in each other. We are described by many of our friends as the happiest, most in-love couple they know. This is because we really know why we are together, now. The real substance to a relationship. The level of trust we have now is beyond anything I could have ever imagined coming out of a marriage eight years ago where I was cheated on. And we are hornier now for each other then ever before in our relationship. Everyday is 24 hour foreplay between us.
He needs to know that you are not interested in swinging because he isn't enough for you, but rather you are interested because of the fun you two could have together. Just take it slowly, talk about it with him (I know making him talk will probably be a chore since men internalize things that are threatening to us), make him feel like a king in your life and who knows what will happen.
I like what others have said about role playing and other things to do together. Maybe rent some porn flicks with group sex or foursomes. Use dildos as another cock in your sex together. Make-up scenarios in your sex play that would be like swinging. Have him read the board with you, and do searches on items that maybe concern him. He may start to like the idea more and more.
Mr. WS