I'm 27 weeks pregnant. Why doesn't my fetus move thatmuch? Is that normal

Probably OK - but... At 27 weeks our concern for fetal well-being is low, because most common pregnancy problems do not arise until after 32 weeks. Having said that, please talk to your obstetrician to determine if a fetal biophysical profile and/or growth/fluid assessment is warranted even at 27 weeks, depending on your risk factors.
Concerned. Usually, 27 weeks is a very active time for babies. Generally, people use "kick counts" as a way to measure fetal health. There are several protocols and one popular one is to make sure you get 10 movements of the baby in less than 2 hours one time each day. Any decreased movement should probably prompt you to call your doctor to arrange an evaluation, though.