Morning sickness easing off is actually a good sign at your stage, though I know it's worrying when the movements suddenly feel different. The thing is, at 16 weeks the baby's movements are still so subtle and can vary a lot day to day depending on baby's position, how busy you are, or even what you ate, so missing a night or two isn't unusual. That said, cramping combined with no movement might be worth a quick call to your gynae or PD just to put your mind at ease, especially since you've been feeling movements regularly. They can do a quick check and let you know everything's fine, which honestly is the easiest way to settle the worry.