I first felt my little girl (who is now one month old) kick at around 16 weeks also.
I wouldn't be too concerned, i thought my baby was having fits too, but it's just the way they move. It's funny when they get the hiccups and stuff, as they feel like little spasms also. It's only natural to worry and 99% of the time, everything is fine!
Good luck with everything though. I hope all goes well!