Ouch. I was gonna post to say that this thread was made for me, based on today's events! But it's actually been a bit of a painful thing to read.
DH and I have literally just had an argument about home-work-splitting... and it turns out you guys (or most of you) are more of his thinking than mine 
DS is nearly 2yo, and DD arrives in March: I'm 31 weeks but she could be early as I have mild GD. Ankles are puffy, hips are painful all day, BP is behaving so far (but I had issues with it the last time) and now I'm monitoring diet and blood sugar level.
DH has always been wonderful: we're definitely 50/50 parents as DS was bottle-fed.
I was made redundant at end of Oct last year, but had a good enough settlement to not seek new employment immediately (given that I was 4 months away from mat leave anyway), and that I still have a monthly 'income' going into our joint account.
Lately, I've been wondering how I incorporate my midwife/HVs advice of 'rest plenty' when I'm basically caring for two people plus myself? I do all the housework bar the one or two bits DH will do at the weekend, which isn't normally a problem but I've suffered PND and anxiety ever since DS arrived, am on ADs for it and being monitored closely by the MW/HV 'just in case', and I've found that too much multi-tasking currently isn't good for me, sends me into depressive symptoms.
DH shares all child-rearing responsibilities, but doesn't understand why my current pregnancy should have any detrimental effect on my ability to do things.
I just wonder, 'if I'm looking after them, who's looking after me?'
But, having read your comments, I now sound like a whiney little baby with no reason to be feeling sorry for herself. I want OP's hubby!
Beaky, I don't think you're being unreasonable to ask hubby about having a bit more of a structured split: but be prepared for him to need to set his needs out as well. You sound like you're both doing a great job, so work on this together to just help your peace of mind