is this crossing boundaries ?

I have no problem sharing with my boyfriend. He moved in with me, I let him drive my car when he needs to. But when we get into it he leaves the house in my car… I feel like that’s crossing a boundary. He doesn’t help pay for my car , car insurance or keep gas in it. I don’t want to throw in his face that it’s mine but I feel like this is crossing the line..

I don’t know how to say anything without his response being anger with me asserting ownership because we share so much..