If your son is living with you it can be difficult to get him removed from your insurance policy until either he moves out or gets his own vehicle and insurance coverage on it. Even though your son will be 18, if he is still a member of your household most insurance companies will require him to remain on your auto insurance policy since there is a possibility of him driving your or your husband's vehicles.
Some insurance companies will allow you to exclude household members, you may check with your insurance provider to see if this is possible. Keep in mind if you do exclude your son and then he was to drive the car from which he was excluded there would be no insurance coverage extended to him.
Another way in which to get him off your policy would be if he has his own vehicle and gets his own insurance policy on it. Normally if you are able to show proof that he has his own insurance coverage like this an insurance company will then allow a household member to be taken off of your coverage.
If your son is ready to shop around for auto insurance, he can start here with us by getting a carĀ insurance quote.