M.O.
Dear Jody,
My son hated the car for about the first six weeks of his life, too, and then he sort of magically grew out of it. I know this may not sound like much comfort while you're still going through it, but I think it's something many babies outgrow.
Whenever we could (that is, when we had one parent driving and another as a passenger), we tried to make the car a space for happy interactions -- leaning back in the passenger seat, smiling, baby talking, tickling, etc. That may have helped my son imprint that the car was a happy place.
And my when-all-else-fails solution (warning: this only works when someone else is driving) was sit next to him and contort my body so I could breastfeed him while he was in his carseat. No, it was NOT comfortable, and yes I did fear being arrested for indecent exposure, but I made a conscious decision that it was more important for my son not to be miserable.
Good luck!
Mira