It's so hard to tell at first!
The first time I felt my son move (1st pregnancy), I was just sitting on the couch at around 17 weeks. All of a sudden, I felt three very sharp, distinct kicks in the same spot - almost like a knock at the door.
I'd never felt anything like it, and I figured it MUST be the baby - what else could it be? But then i didn't feel anything else for a couple of weeks, and when I did feel movement again, it was those indistinct bubbly feelings, not sharp kicks.
So, who knows? No point worrying in early weeks. It's not till the third trimester that there's any concern about baby moving or not.