If you aren't comfortable with this then don't feel pressured to. I am friends with a couple that has an open marriage and for them it works and they are very happy, they are also very open and honest with each other. It works for some but not others. I have tried an open relationship before and it just wasn't for me, I am very possive and I want to be the only person. Talk with your husband why he wants to try this, what ground rules would there be? Also ask yourself how you feel about this, imagine what it would be like and how you would feel. Your feelings are important and your husband should respect that. Best wishes to you.