Thanks everyone for your words of wisdom. I suspect the problem is that I am really not a very domestic person (I am a great cook, though!) and I find being at home very hard, as I feel the pressure of expectation to do domestic jobs more keenly. The asking for money bit doesn't help either but I will go back to DH with some of your suggestions. I think, really, that secretly I would really like to go back to work but feel too guilty about doing so as I was off for 12 months with DD and feel that DS deserves the same, especially as I work full time (albeit flexibly). It's the whole 2 naps a day period where getting out is hard, I didn't enjoy it last time but I think it was the right thing to do.
Anyway, you are all very kind and it makes me feel better to hear that others hate it too. I think there are some people for whom being at home and organized and lovely is not effortless, but certainly not problematic - they're just built that way! I'm....Not.
I like the timer idea, and will implement.
DH is also doing my head in by complaining about the mess and constantly changing his mind about whether or not I should return to work early and offering contradictory reasons. I am not sure he really gets what it is like to be home full time, he really does think maternity leave is kind of a holiday 
ApuskI DD did projectile vomits till 4 months and vomited all the time till 6 months, I was constantly wearing clothes with unnoticed bits of baby vomit on them. My sympathies.
LTEC don't suffer in silence!