I'm babysitting- How do I help this baby not spit up so much?

He’s 6 months old and cute as a button. It’s been an hour and a half since he ate (formula) and he’s still periodically spitting up. Mostly little amounts, but some are much more. I finally got him to go down for a nap, and now I’m paranoid and keep checking on him in case he spits up in the crib. Poor thing…

His mom warned me that he spits up a lot. I stirred the formula instead of shaking it to minimize bubbles. He burped well after feeding. I’m careful not to jostle him too much after. We’ve both changed clothes twice today (He spit up all down my back, even though I had a burp cloth on my shoulder).

My son wasn’t like this, so I’m feeling like an idiot not knowing what to do. Is there a position I should be keeping him in? Am I not burping him enough?