9 month old arching back crying when i need to wash her or dress her or even put her in a car seat. no flu and nose clear no fever no cough i'm not sure what this can be but shes very uncomfortable. please help?

Behavior issue: Infants have a limited ability to communicate. They learn early when you do most everything they want/need quickly (feeds, attending to cries) that fussing brings results. When you do something they don't agree with they protest the way they know gets attention. I would not assume she is ill or hurts. The behavior will fade if you do what you need to do & fussing does not stop it.