No movement at almost 20 weeks?

I am almost 20 weeks pregnant with my second child, and I have felt no movement at all, at least not that I have noticed. I had an ultrasound on Tuesday, and she is just fine. I even have a doppler, and can hear her kick all time, but I can't feel it. I felt my first move around 17 weeks, and I'm not overweight, so that isn't the case. When should I be feeling her? Is this normal or could there be something wrong with her?