my SO drives like a f**kn maniac

I love this guy I do and he's a good boyfriend. The only problem I have with him is that he drives like a fucking idiot. To the point that I choose to follow him in my car because I can't stand the way he drives. I feel safer driving myself behind him. Tonight I watched him almost rear end two cars on the highway because he follows way too damn close. I tried talking about it but he doesn't see an issue with how he drives. I don't want to get a phone call one day getting told my boyfriend has fucking killed himself on the highway or someone else, I literally stress out about it. It drives me insane, I don't understand what's going on in his mind like this shit is dangerous and he's not invinsable. He's either gonna end up losing his car by totaling it or getting killed and I don't really know what else to do. I can't control how he drives!?