There's an absolutely massive growth spurt at 4mo where many peoples in they have to reintroduce another NF. It's just for a little while. Just make sure he's leaving an least an ounce of two in his bottles during the day so you know he's stopping because he's full and not because it's run out ok? It usually sorts itself out within a month. It is one of the biggest GS.
That being said, the GS also coincided with an awful wonder week (do you follow those?), usually called the 4mo sleep regression. It's a yucky time. Short naps and more awareness.
I would abandon pu/pd and try ssh/pat as I mentioned before. Keep the room dark for the NW and do feed if it's been more than 4hrs since the last feed. It's a case of being consistent during this yucky time I'm afraid. We've all been through it and come out of the other side. For us, it was the 4mo SR and the 18mo SR that was the worst. As you're only on day 2 I would hold these times for another day, use ssh/pat to try and extend the naps if you can and just try not to go too crazy
. Let me know how it goes today/tomorrow then we can look at tweaking again. If we're looking to extend A times (which it looks like you're trying already) we like to give them 3 days to settle into it and reassess again. Here to hold your hand xx
