Although your partner has to do the heavy lifting himself, there are things you can do to help make his work easier. The first is to listen. Nobody wants to be jealous. Nobody enjoys it. Your partner isn't doing this to hurt you, or out of spite. So listen, compassionately, without judging or shaming. Allow space for him to feel what he's feeling. Remember that saying "You shouldn't feel that" probably won't change anything. Creating a safe space for your partner to talk openly about his feelings goes a long way toward making a solution possible.