It is amazing how things like that happen, I've known others who took ages to conceive their first and ended up having three in quick succession.
I can imagine how scary it is for you, most of us wouldn't want such a close age gap but it's happened.
Are you financially comfortable enough to be able to afford some help at home with the children and housework? General 'mother's help' sort of post. Or maybe your mum or mum in law. It would mean you not being completely worn out all the time. My cousin had three children very quickly but had great family support, it's hard to do it alone.
I suggest you sleep in the other bedroom with the new baby while he or she is very small and let your older one - who won't be very old - stay put in your bedroom with your husband asleep there. You'll still have time for 'get togethers' when both children are asleep but we all know the early stages of babyhood often involve sleepless nights.
Once the tiny one is settled you could bring her into your room and later suggest to your eldest that she might like her own room, make it exciting for her but don't force it because little ones are sometimes nervous at night if they wake up and there's no parent present. I realise the chances are you'll end up with both in your room for a while but that won't last forever. They can eventually share a bedroom but I expect you'll be looking for a bigger house at some stage.
These are just ideas, certainly not advice which I would never give. You will work something out. What I wish for you is an easy pregnancy and delivery of a contented child.
It really is wonderful news even if it doesn't seem like it at the moment and I wish you, your husband and Big Sister many congratulations.
