Decreased fetal movement

My little guy is usually very active. I usually do kick counts after breakfast or after dinner bc he's always very active around those times. I can usually get 10 in about 20-30 min. Yesterday, I noticed not much movement so after dinner I decided to do kick counts. It took a little over an hour to get 10. Today, after breakfast I decided to check again. After eating, drinking juice and laying on my left side for almost 2 hours I only had a few kicks. My dr had me go in and be monitored. It took several hours to get him moving but everything looked good on the ultrasound and his heart rate is good. I'm glad all checked out ok but my doctor stressed that babies do not not stop moving bc of lack of room. It's always a good idea to go in and get checked bc as mom's we know our babies already and how much they usually move. If ever in doubt go in don't wait.