20 weeks babys not moving??

Krystin • Im 19 happily married with our first baby boy due in april!
Okay so I'm only 20w3d and I normally can feel my baby boy kick. Well I think I felt him kick this morning and my mom found his heart beat on our Doppler but he moved from it but he hasn't kicked me is this normal like do they have days were there just kinda sleepy??? Please I've been having dreams of premature labour.