spit up

So it's been happening for awhile but my baby spits up/vomits his milk quite often. More than often actually it happens a lot! It doesn't seem to be digested either it looks just like his milk! I burp his every 2oz like the doctor says and I feed him in an angled position so I'm not sure what's happening. And this is the weird part, a lot of the times he spits up literally 10 minutes (sometimes longer or sooner) after his feeding and it's still straight milk! I would think it would be digested by then so it should've looked chunky. It used to be that way when he spat up but not anymore. And it's not dribble spit up its sometimes projectile or a waterfall. Any suggestions? I tried changing his formula and it doesn't work!