I too am 18wks and I feel my little girl kicking every now and again. Usually on my bladder. This is my third baby and they say you can feel them sooner with each. It also depends on where your uterus sits also. I wouldnt worry about it at all!
YES ITS TO SOON I REALLY DIDN'T START FEELIN MY DAUGHTER MOVEMENT UNTIL I WAS ABOUT 22 WEEKS