With a fifth pregnancy, most mums start feeling movements a bit earlier because they know what to look for, so not feeling anything at 22 weeks is worth flagging to your gynae or polyclinic, just to get it properly assessed. The low weight finding at 20 weeks combined with no movements felt yet are two things that are better checked together rather than separately, so I would go back sooner rather than waiting for the next scheduled appointment. Your doctor can do a quick check on baby's position and activity, which will give you a much clearer picture than trying to guess from the outside. It is always better to get peace of mind from a professional, especially since this pregnancy does seem to be tracking a little differently from your previous ones.