Have you been to the Dr.? You may be farther along, they can tell by an u/s. But as far as movement I think every person is different and it is possible that your feeling movement this early. M best friend with her first felt movement about this time also. Good luck and let us know...
Is this your first pregnancy? It does seem soon for a first, but anything's possible. You could request an ultrasound if you're not sure of yor dates or think you're further along. If this is a subsequent pregnancy, it is not uncommon to feel the baby move a lot sooner. I felt my 2nd baby at 13 1/2 weeks pregnant and felt her move on a daily basis at 15 weeks.
This is my first baby and I felt movement around 15 weeks - not regular, just one single kick. I didn't feel it again for another week and then it was just one kick again. After that it started to happen a bit more often but it certainly wasn't regular or noticeable until around 18 weeks. Perhaps you are further on than they think!
I have heard that slimmer women feel the baby sooner. You have been very sick so I imagine you have lost alot of weight and I would say that is why you feel the baby sooner. I felt mine pretty early too on a regular basis. But like the other poster mentioned, did you have an ultrasound to see if the dates are correct?