Should I be worried?

I'm a ftm, and 17 weeks pregnant. Usually my baby is pretty active during the day, and not so much at night. Last Friday I stayed up past midnight (I'm usually asleep by 9:30) and the baby was awake as well. Since then, the baby isn't so active during the day, and I'm not sure if it is at night, because it's kicks and movements aren't yet strong enough to keep me awake. Should I be worried, or is this normal? What was your experiences?