My 7 wk old DD HATES her Britax Marathon car seat!!!?

I received this car seat as a gift from my parents and was very happy until I put my baby in it for the first time. She is cool for a short while with me in the back with her, but soon enough, see is screaming her heart out. I think that it would be cruel to let her scream,because she is a precious, innocent baby who need to feel secure. But I have to go about once in a while. I usually have my older daughter sit in back w/her to give her a pacifier (I don't care for pacifiers!!!) Has any one else experienced this with the Marathon?