It could just be the way the baby is facing. With my daughter I hadn't felt her for almost a day and went to the ER scared and they did a NST (monitors feral heart rate and movement) and they couldn't get a good strip because she was moving too much. My OB said it's because she was facing my back and everything is fine. Now I just assume this guy is facing my back when I don't feel him for a while.
Drink water, play music for her.. try to watch a light family movie.