I would seriously consider the PGD route... knowing that you both carry the Delta F508 gene, it is a very prudent thing to do. Especially since you and your husband do not see eye to eye on risking a natural conception. You do not want to put yourself in a "I told you so" situation with him if you happen to persuade him into it and then you did end up with a child with CF. Having a child with CF can take a toll on a marriage and if he was against the idea of risking another pregnancy in the first place, you will be putting a serious strain on your marriage.