Sometimes as your baby gets larger towards the end of pregnancy, they seem like they move less because there is less space in there to really turn and kick. Also as the baby's head moves down lower into the pelvis, they're less likely to turn or rotate.
If you've felt no movement in 3 days, I would definitely suggest you contact your doctor to have things checked out as soon as possible. Your baby could be fine, or they could need intervention. The sooner you get that reassurance or help the better for you and your baby.
Wishing you the best!