D.O.
I do remember those busy days and sleepless nights--they can be exhausting. The light/day suggestions are really good, although honestly she is so young that you might wait another week or two to balance those out. Remember where she came from, that warm, dark, mommy place of safety. It seems normal to me that she would want to be stuck to you right now. All this is still very new to her, too.
When you become engorged, pumping will help, but I suggest that you not express a lot of milk unless you want to use it in the future (daddy give bottle in evening or at night??). I would pump enough to ease the pain but no more in the first month, because I found that if I expressed more than an ounce or two it aggravated the engorgement by causing my milk-producing glands to overproduce. I guess they thought that the baby was consuming all that breast milk!
It is difficult to focus on your new little girl when you have a very active four-year-old, isn't it? Are there ways he can help? My eldest daughter was 17 months when number two daughter was born, and even at such a young age she was a great assistant, holding the baby while she watched "Mr. Rogers," or bringing me things I needed while I was nursing the new one. When baby boy came along three and a half years later, I had two marvelous helpers built in. They were never responsible for the baby, just always included in his care somehow. Additionally, I took my infants outside within a week, even number one, who was born in early February. She came everywhere with me, and though she napped for at least two hours each morning, she was often wakened from little snoozes during the afternoons and evenings. During those periods she would nurse about every two hours. She, too, confused day and night, but not for long. In fact, she was sleeping 6-8 hours a night by six weeks, and 12 hours a night by three months.
The sling was a great salvation with my son. I think he lived in it for a year or so...and with two other young children I was quite grateful to have and use it.
The girls differed from him in that they would sleep on me, near me, next to me in our bed. He never enjoyed sleeping in close proximity to another body as an infant; he would nurse, doze, and then fuss until left by himself. I treated him like my daughters at first, but he did not sleep at all. After three exhausting days postbirth I finally (tearful with guilt!) put him into his bassinette, at which he squirmed for 30 seconds and then fell asleep for four hours. He did not sleep with us until he was a toddler having night terrors, at which time we let him into our bed just to keep an eye on him at night!
Rest when she does, eat regularly, and enjoy the closeness now--I remember the amazing changes each infant underwent each day, a gift to behold because I was home with the children. This time will pass quickly; it's only temporary. You will be able to sleep again for more than an hour or two, so try, if you can, to relax. If you can, perhaps she will, too.