Baby Projectile Vomit

My 11 week old baby just projectile vomited. At 7pm he was acting really fussy and hungry but I had no more breast milk so I made him a little bit of formula. He had about 50ml (1 1/2 0z) and he seemed like he was good. Then at around 8pm I pumped and had fed him about 50ml more of breast milk. Its pretty normal for him to cluster feed right before bed so I didn't find the amount that he ate to be out of the ordinary. He was pretty restless from 10-11:30pm and was squirming and hitting the side of the bed. I got up to pump again and while I was pumping he projectile vomited in his bad while lying on his back. It came out of nose and everything. My husband and I sat him and watched him and he kept making this face like he still needed to puke. Its 12:15am now and he's settle down and laying beside me sleeping well, but im too scared to fall asleep and feel like I just need to watch over him a little longer.

This is only the third time he's had formula. The other two times he had it he was fine, but do you think it was formula? Do you think maybe he was over fed? Its been super dry here with the santa anas coming in and we are all super congested with bloody noses, maybe it had something to do with that?

Im a FTM and this is the first time anything like this has ever happened so Im a little freaked out.