Poor you. Hugs. I think you are amazing to have 4 kids.
If you can bear it, as the other posters suggest, try just "wear" the baby - a loathesome expression - but it sums up that you forget about the baby. I put mine in a meitai for about 6 months solid (except, as someone said, for showering). They are very comfortable, washable, light, available second hand, you can bf in them, and useable until the baby is a toddler (though by then you will be using it occasionally, and on your back - don't worry, you will not be wearing your baby for ever, only while it is little and light).
Whether you use a Meitai or other carrier, they helped me a lot because I found that a big stress was trying to put the baby down, and inevitably being called back by wailing and squawking. Looking after a toddler with a sleepy baby on your chest is quite nice, certainly better than being howled at. If your other dcs are out or otherwise engaged you can even curl up in an armchair and nap yourself, you are more likely to get some rest like this than trying to put the baby down (disclaimer, someone will prob come on now and say this is VERY DANGEROUS but I don't mean real sleep, just sort of closed-eye down-time).
Bronchiolotis is a big eveil GIT. Have you got all the drugs? when my dd1 had it she was on anti-bs, calpol, and an oral version of ventolin. The last really helped her breathing. It's horrible. Sympathies to you and your baby.
While the baby is snoozing on your chest, make a big cup of coffee and sit down to do a huge online shop. Buy ready meals for a week, or as many weeks as will fit in your freezer. Get some nice chocolate and some wine. Get as few things as possible that need any sort of preparation and as many things as possible that can just be eaten: stuffed pasta, pesto, pieminster pies, bagged salad, baked beans to go on baked spuds, covent garden soups, that sort of thing. Arrange for it to arrive at a time your husband is in and get him to put it all away. Set up a weekly delivery slot and then you will just have to do "maintenance tinkering" on a weekly basis.
Get someone to take the baby out, and have a nap. Even as a one-off it will really help. Don't be fobbed off with you being sent out to "have fun". You need a rest, in your own bed. Even if your dh or whoever is pounding the streets with a pram for two hours solid, do not let them complain about it. You need that two hours.
Get into a really good DVD box set. You can watch this in the evenings when your older kids are asleep with your baby on your chest in the meitai if necessary. this will feel like something to look forward to even if the baby is still with you, even better if your dh gets into it too and you can hold hands and pretend you are at the cinema. But better, because it is a series so there is always something nice to look forward to at the end of the day. What sort of thing are you into? Have you seen (not really focusing on current stuff, just stuff I have really enjoyed): The Wire; 6 Feet Under; Buffy; Deadwood; Justified? These are things I like but you go for SATC or Morse or whatever floats your boat.
VERY VERY BEST OF BLOODY GOOD LUCK TO YOU, YOU ARE A HERO