I think those feelings are pretty normal. I personally went the other end of the spectrum with my hubby... I was way more experienced and that was one of the reasons I enjoyed swinging. I felt bad that I had so much more experience and liked the idea of swinging as it gave him a chance to "catch up".
I don't think you have anything to worry about. Just keep in mind the biggest difference between sex and making love is the love part. As long as he loves you, the "sex" the two of you have together will always be the best in his mind. No "sex" can match what you get when you combine two people that are in love.
If this is something that you want to happen the best thing you can do is be open with him about your feelings. Let him know about your insecurities. And if you do take the step to start swinging and you start feeling jealous or insecure, talk to him about those feelings when they occur. Even if it means stopping in the middle of playtime to have a discussion. These aren't issues you want to let fester.. they are things you want to discuss right away.
Julie
http://www.swingersboard.com