Hi T..
I'm not pregnant now, but I have a very good friend that is. She is about 22-23 weeks and she really doesn't feel alot of fetal movement either. Her placenta is actually in the way. Her doc also told her that every pregnancy is different and some you wont feel until as late as 28 weeks. If you are overly concerned, no harm in calling your doc.
I hope you have a relaxing pregnancy as added stress isn't good for you or your beautiful boy! I know it's easier said than done though. I lost a baby mid pregnancy and I know all too well those moments of extreme worry. You just need constant reassurance that everything is okay!
Goodluck and relax! Pretty soon he'll probably be using you as a punching bag!
Congrats,
H.