Scared. Please help.

Alyssa
I'm 21 weeks pregnant and a first time mom. I haven't felt my baby move today. I'm really scared. She was moving around a lot more than usual around 3pm yesterday. It's almost been 24 hours and I haven't felt her since yesterday evening. Am I being paranoid or do I need to go to the doctor? Please help me. 
Just for a little background, I was rear ended last Thursday, almost a week ago. We went to the hospital and she was just fine. I'm so scared and worried.