It never hurts to go get checked. Usually once those monitors are on babies love to move a ton. If you are dehydrated or eating less due to being sick it could affect movement. Try not to stress I’m sure things are good but like I said doesn’t hurt to get checked!
A heartbeat isn't the only sign of health for a baby, if you think there's decreased movement, you should go get checked out. Better safe than sorry.
If there's been a decrease in baby's movement you should go in and get checked