Hey Michelle - I had the exact same issue a couple of weeks ago (I would have been about 24-25 weeks pg). Bubs went quiet all of a sudden. I went to the hospital and had the midwives check it all out. There were no probs...bubs heartrate was great. They said that it happens sometimes for various reasons. It was really hot at that time, and bubs could have been feeling lethargic (her mum was certainly feeling the heat), sometimes apparently they slow down during a big growth spurt, or at this stage in the pg they are still fairly little and if they move position and face a different way, you may not feel their movements (especially if they are facing away from your navel and kicking your insides where you don't have touch receptors!).

Hope that helps to put your mind at ease a little...I would always suggest going to see the midwives at the hospital and asking them just to check you out. No need to be anxious, if everything's fine!