Big hugs. I've been in a very similar situation.
I started giving my DS a 'special box' for when I was getting bub to sleep. It has toys in it he really likes that only come out at baby sleep times to keep him quiet. Or I'd put on a DVD and give him a snack.
But yes he'd still come in at times wanting something and I'd often lose it too. It's very hard trying to manage it. He'd bang on the door and scream if I closed it. But he's really improved with time, baby is 9 months now.
For the days their naps didn't sync up I'd feel like crying, so tired.
DH and I would often argue about it all too.
If.you have anyone else to help give you a break for an hour, tomorrow if not today, then try to arrange something or do something for yourself when the kids are in bed, bubble bath, glass of wine, whatever you want.