I am the owner of my car my new boyfriend what's to be a Co owner of the car because he drive it the most should I let him

Not only NO! ...but heeeeeellllllllllllll NO! When you get married he can be on the car - until that day - you keep ALL your finances separate, every penny every dime, and you DO NOT co-sign or commingle credit AT ALL.

There is no reason for him to be the co-owner. If you add him to the title and then decide later that he is not the person you want to spend the rest of your life with, removing his name may be a problem. He can drive your car as much as you want him to do so. He is listed as an additional driver on your insurance, so that is covered. If you need an excuse, tell him, "Baby, if your name is added, we will have to pay extra money to transfer the paperwork, and if something should happen like an accident while I'm driving, they could sue you, too."

Three very smart lawyer have told you "no.". I hope that pay attention.