Try not to worry if you think baby isn't moving much, some baby's don't move alot at all and aren't very active kwim? Having an anterior placenta wont help either as most of the kicks etc will be cushioned by it. It was really from about the 22ish weeks mark that I started getting the constant strong movements that you could feel whether you were moving, sitting etc. As baby gets bigger and stronger, you will be able to feel the 'pushing/stretching' type movements where baby tries to see how far he can stretch across your belly LOL.