Thanks everyone - this thread and all your responses has really got me through the last few days. I was SO SO down when I first posted, but glad to say that I now feel a whole load better. As CAM said, i think it was the sudden shock of my Mum's news that hit me hard and was 'the straw that broke the camel's back' so to speak. Thanks for all your excellent suggestions - I'm trying to take many of them on board.
Fortunately we all seem to have got through the worst of the colds/flu/bugs now and I'm getting some decent amounts of sleep again (OK - well about 6 hours at least!). However DH and I recognise that we can't just go back to the same situation and wait for the next thing to knock us for six, so we've at least made some immediate changes and decisions.
When we had DS2 we seriously considered the Nanny route, but decided against it on the basis that DS1 just LOVES his Pre-school and has lots of friends there, and I think would be heartbroken if we took him away, and we probably can't justify the cost of both a Nanny for one child and nursery for another. However we HAVE decided to get another au pair (used to have one until a year ago) which means that all cleaning & ironing gets done, she can help with bits & pieces of childcare while we're around, and we get two nights a week babysitting to give us a chance to go out and have some fun again.
Amazingly just after I posted first we were contacted by the sister of another au pair we know asking if she could come and work for us!
I've gone through my diary at work and taken out or delegated all 'non-essential' meetings and travel and told my team I'm not prepared to be away from home for the next few months unless absolutely necessary. I've also booked out some days holiday in the next few weeks for myself, and dh and I have booked a weekend away for all of us in March. I don't really feel ready to ask to reduce down to 3-4 days a week just yet, but that IS my longer term plan once I know the job better.
Actually I was really pleased to find that when we were willing to admit to friends and family that we were struggling, suddenly quite a few people rallied around for us without us having to ask. Some friends of ours took DS1 off to 'soft play' for a morning, and DH's parents asked if they could come down for a few days in a couple of weeks to try to help us.
And finally my Mum had her first Chemotherapy today and when I spoke to her she is sounding much more positive about the whole prospect. She's such a brave woman...
So anyway, at least I can see a little light at the end of the tunnel.
Thanks again for all you support out there - it really does make a difference.
(SB34 - thanks too for your kind offers of help. As I say, I think we're through the worst, but it would be good to catch up with you again at some point anyway - I often think of you - especially now that DS2 practically lives in the Rocking Entertainer!)
Oh, by the way - for those that asked - I'm in Surrey - Redhill/Reigate area.
Thanks everyone - you're a fab bunch of cyber-friends.