I think its different for all woman, so I can only speak for my own experience. I started initially feeling movement at about 18 weeks, but it would only be every few days. I am now 20 and a half weeks and I feel her moving around every day. The U/S tech told me that when you are up and walking around it can rock the baby to sleep, so you are more likely to feel them when you are lying down when it wakes them up from you not moving.
Re: Movement