I feel movements ALL day like you explain. After watching my son sleep (who's 2 now), I'm convinced that some babies move while sleeping, although it's stronger movements and more frequently when there awake. I feel kicks/punches to my bladder several times an hour. I actually get up and go for short walks when the baby's getting too active because when your walking sometimes you can get the baby to move positions or even fall asleep.
It also depends on how the baby's sitting and where your plecenta is. If your plecenta is in a place it can "hide" some movements until the baby's larger so some mom's don't feel as much.
By 28 weeks you are supposed to feel 10 movements within a 2 hour time frame. Like all people though babys have their active days and they're lazy days so some days you may feel them more than others. It also depends on baby positions and where they are kicking if you are going to feel them or not. I believe during this point in pregnancy babys sleep in 15 minute increments. Also by 28 weeks the baby is getting so big that its hard not to feel all their little shifts and what not. Its also why doctors suggest not starting kick counts until 28 weeks. You'd be shocked how much babies move and you dont even feel it!
Babies each have their own schedule - and their schedules can change from day to day. Some move while they sleep. Most women I know who say their babies move "day and night" don't mean that it's constant movement every second of the day. They just notice it at all sorts of different times - including nighttime. But, some women might notice movement all the time - or movement plus gas.