Decreased movement?

I'm 23 weeks pregnant right now, and my daughter is usually pretty active. I normally feel her everytime I eat, drink, sit, or go to bed. Yesterday I only felt her once, and today I have not felt her move at all. It's really worrying me, and my doctors office Is closed on weekends, and they have never given me an "on call" number. I don't know why they haven't. I'm trying to avoid the emergency room, but I'm really worried and scared something has happened to my baby girl. I'm just trying to figure out if this is "normal" before going to the emergency room.