Help!

I'm currently on a short (1:45) road trip. My 3 month old is usually great in the car. Now he is screaming bloody murder. We pulled over, I changed and fed him and he calmed down when I was holding him. Then we put him in the car seat again and he started right back at it. It's breaking my heart and we still probably have 45-60 minutes left. Any ideas for help? Obviously I am not the one driving right now. I'm actually sitting in the back seat with him.