Let him know how u feel. Personally I think it’s best to abstain until baby is more stable (after first trimester). While there is no restrictions on whether have sex or not it’s best to err at side of caution. Have seen many cases of mummies getting bloody discharge or miscarriage risk from intercourse. Of course it’s still you and your husband choice. For me and my husband we abstain from intercourse 100% as we didn’t want to risk the pregnancy at all. Many parents also choose to altho there isn’t right or wrong. Just be prepared for any negative consequences happen to your baby.
Even if you do not have an underlying condition (Eg pregnancy), you should be able to gently reject your husband if you are simply not in the mood. It takes 2 to enjoy sex, and good communication is part of intimacy in a relationship. Just tell him how you feel, you can always satisfy him in other ways aside from insertion.