diapers for blowouts?

Allison • Wifey to 👨🏼‍🦲, mommy to 💙👦🏻, ivf warrior 💉, 🌈 baby 💙👶🏻
My son (20 weeks) has been having bad blowouts these past 2 weeks. Every poop has been a blowoit up the back of his diaper. He's already in 3s and about 18 pounds so I don't think he needs to go up a size but we are probably Gona get a box of 4s just to try.
He normally wears pampers sensitive and we just tried target diapers, and they were fine but still having the blowouts.
Oh and they happen no matter what position he is in (sitting, nursing, laying down etc...)
Suggestions?