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! :)
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.
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.
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. :)