i wouldnt worry about it cause im on baby number 5 an i didtn feel this one move until i was like 21 wks. i felt maybe a flutter once or twice but that was it! so i wouldnt worry about it as long as they are hearing the heart beat you are good. :)
I felt my baby at 14 and a half weeks (first baby) but I don't feel him/her consistently. I think it depends on your placenta and where the baby is kicking. If he/she is kicking in a less sensitive area you might not feel it.
17 weeks is pretty early to feel movement. You may have and anterior placenta, or a placenta that is in front. This makes is harder to feel movement... like trying to feel tiny baby kick through a pillow. I have this type of placenta and at 21 weeks I am just starting to feel a little more movement. Good luck.
At that point they are still small enough to hide. Hence why they say not to do kick counts until like 28 weeks. If you are at all concerned though I would contact your doctor and see if they can find the heartbeat for you since that should be more reassuring. Congrats on your pregnancy! :)