sounds like the baby to me! and like 30something said, it will start getting stronger and you'll know for sure in another week or so (in my experience... it may take longer, though).
Yes; last week i thought it was just gas but now i can feel it really good like something popping like popping. And this is the first time i been pregnant this far so im not sure of this feeling.
IT is ahrd to say. If you are sure it is not gas then I say it is the baby!!!!! You should feel movments by now unless you are very over weight in your belly. Woman say different things about how the movments feel but I woudl guess that if you are writing this then you know it is not gas:) They will only get harder too!