Am I just being paranoid? :(?

I'll be 20 weeks pregnant on Monday. I have been feeling the baby move more often lately.. Not a ton but flutters here and there throughout the day. Today I'm not sure if vie felt him at all? I may have and can't remember.. But regardless its much less then the past few days. Should I be worried? What could cause this? And what effects can caffeine have on my baby at this stage? I ask only because I had a few glasses of coke yesterday and a few today..