No movement yet at 17.5 weeks

Danny

17.5 weeks with baby no2, a boy. I still haven't felt any movement, except for random little flutters here and there. Some days, I don't feel them at all. Should I be concerned? When did you all started feeling anything and did it make a difference that it was your second or third pregnancy? I just had my ultrasound at 17 weeks and baby was fine and active. I can't help but worry especially since it's my rainbow baby.