Need help with baby name! Husband and I don't agree?

We are expecting a little boy, my first boy, 2nd child. There were several names I liked, but when I approached him with my favorite, he liked it but kind of changed it. The baby's name was going to be August. He took that as short for Augustus. I said no, just August, no US at the end. He said he liked it with the "us" at the end, he didn't like it without. He says its a roman emperor, all I can think of when I hear Augustus is the fat kid from Willy Wonka. I can't STAND that he wants to call him that. I agreed to put it on the birth certificate but I told him I would never call him that or ackknowledge that that is his name. I'm only 7 months along and he keeps telling everyone his name is Augustus and I get so mad and correct him. Now, I'm thinking I don't even want this name if he is going to mess it up! I don't know exactly how to tell him how much I hate it and how much it upsets me. I playfully correct him and get "mad", but I don't think he knows how much it bothers me and the other names I liked, he really didn't. I'm very picky with my children's names, I have to call them that the rest of their life! Guess I'm asking what to do and how to approach him without hurting his feelings, I love him dearly and its his first child and only child. help!