Should i be worried?

cc
So i started feeling my baby move at around 16 weeks. No not gas,my baby when i layed on my back for a few minutes a ball would go on my right side&move(i know it was my babies head also im not a 1st time mom. But anywho, for the past few days (3 days) I havent felt any movement and im starting to worry since my baby was moving every night. Any experiences?