Reduced fetal movement

So for awhile it seemed like my baby's kicks were getting stronger and more frequent the other day she was practically doing somersaults. But now her movements seem lighter and less frequent I mentioned this the first day it happened and I was at the doctor anyway. Her heart beat was normal. I can count the number of kicks you're supposed to but I can't help but worry because they're not as strong. Has this happened to anyone else, is it normal? The nurse I asked wasn't very reassuring.