Vomiting large amounts even after burping...what am I doing wrong!?

My LO is a week old today and has started another round of cluster feeding- which is perfectly fine and dandy(other than the fact that I am fall-on-my-face exhausted all the time because he wants to eat like every hour.) I'm starting to dread laying him on his back to sleep though- because he keeps vomiting up food even after 45+ minutes of burping him! He doesn't do it every time but often enough that it's starting to freak me out. Last night he was asleep for over and hour when it happened and it looked to be about 2oz of breast milk! All.over.EVERYTHING.

Am I just doing it wrong???

I've tried burping over my shoulder, laying him on his side, and holding his head up with him leaning forward and none of them seem to make a difference.