My DD was doing a lot of projectile vomits at around 5-6 weeks so we suspected food allergies (and we were right). My DD had green stools mostly.
Maybe you should talk to your pediatrician, but maybe you can try gripe water and a tummy massage at first to see if it may just be a little gas. If the vomit and pain continue and her stools become more green, then I would also suspect that there may be something food related going on.
But, I could also be biased due to my own experiences... so I don't want to sound like an alarmist. Tummy issues and gas are pretty normal around that age. Go with your intuition.
Me: New mama to DD born 11/17/2009. We And: