Hi Jan
I had a similar stress to you earlier in the week. I was going to ring the hospital but movements picked up and so I raised it with my obs yesterday. He indicated that depending on the babies's position, I might not feel the movement as what we feel is usually reverberations of movement in the uterus which affects other organs (eg stomach) ie if bubs is actively hitting the back of your uterus you are less likely to feel it because the movement is stifled by your internal organs.
If you are feeling really worried and can't get your ob ring your hospital, they will see you to monitor you and ring your ob if there is a problem which i am sure there isnt.
I am sure its all ok
Take care
B