You and Shel need to sit down calmly and discuss what you both expect and come to a comprimise, yes you are both in this together and yes it is both your responsibilities, but Shel is out there working and i don't know what she does as a living but she is taking responsiblity and providing for her family.
When our DS was a baby i was the one that got up to him during the night and he was FF from 1 month, because DP had to get up and go to work, at least if i needed to i could nap during the day when DS was, where as he couldn't and still can't. DP had a fairly physical job at the time where he also needed to have good concentration.
When this new baby arrives it will be the same and considering he has changed his occupation and is now a Boilermaker i would hate to think that something happened to him because he was so tired and didn't concentrate on something he was doing.
But also there is only so much a person can tolerate before she burns out or loses the plot so to speak and sometimes you just need a little help and Shel should be there when these times arrive.
Best of luck