Oh! How horrible for you!!!! Big
for such a sick baby! Good for you for still nursing...of course, since this is your fifth, it's probably easier to nurse than do bottles at this point.
But on to the advice: IMO, this is perfectly normal. All my babies have hit a wicked, and I mean wicked, growth spurt at three weeks. Constant nursing, fussing, nursing, pooping, nursing, nursing, nursing. Exhausting! I bet your baby is doing that same thing, on top of making up for lost time in the hospital! As far as the letdown, most babies get a handle on an overactive letdown with time. However, if you think it's impeding her growth because she's not getting enough hind milk, then pump out that overflow and then put her on to nurse. What a pain, huh? If not, then just nurse her only on one side for several feedings in a row. I do that, even now, at almost 11 weeks, because I have such an abundant supply. Like I'll nurse dd at 3:00 on the left side; she nurses for about ten minutes and falls asleep. At 3:45 she's back up and I nurse her on the left again. Then, at 4:30, when she's hungry again, I'll put her on the left side. When she pulls off that side, then I'll put her on the right and start the whole process over again. Exhausting! Whew, I'm tired just thinking about it. Obviously, my baby nurses a lot.
Anyway, don't know if that answered your question or not...as far as getting anything done, well, I only have four kids and get absolutely nothing done, so you're doing great if you can with five! I'd say just make nursing a priority (or as much as you can with four other children) and get her through this growth spurt. Good luck and hth