I've had this with both of mine, can't sit up behind the vertical (never mind lay back!) for about 3/4 days post section.
It's the worst pain I've ever felt ever, and I've been through back to back labour 
It had me on all fours literally screaming on the ward, I couldn't even reach to the call button, couldn't move or breathe, they just heard my screams and came running. And I hate to make a scene.
Both times I've had oramorph (morphine) which has sorted it, and then just been VERY careful not to sit back at all, as that's what sets it off.
It's crap having to sit up all day and night after a section, I hardly dated sleep in case I sat back in my sleep and set it off again. I also stayed in an extra night each time as I wouldn't have been able to deal with it without morphine.
It was by far and away the worst part of having sections. I have nerve damage in my shoulder anyway so that might be why it's so bad.
Anyway when it comes on strong just ask for demand oramorph, and then be careful not to sit back.
Once you get rid of the wind, it does go completely though. Hang on in there!
Oh and congratulations! 