I really don't know exactly, you just kinda keep on truckin' for the most part. My DD was a frequent feeder for a very, very long time including overnight (4+ wake ups till 2). When she was little I'd just set up the couch with my laptop, some good DvDs (or TV shows), something to read, a huuuuuge bottle of water and snacks (I ate a lot of cashews and peanuts haha). It is really hard to eat properly when you are chained to your butt so that could be why you feel run-down. I always did the big bowl of porridge in the morning, with some banana and that could keep me going for ages with snacks and water if neccesary (such as DD wouldn't settle at all till mid afternoon when I could finally grab something else) but definitely, yeah, try to eat when you can.

I think the hair thing is pretty normal, isn't it something to do with how much you retain during pregnancy (you know, that luscious pregnancy locks) and then the 'fall out' has to catch up? I don't know, could be making that up. At any rate, you having vitamins won't affect your breastmilk negatively... it will just put in what it needs, its smart and stuff; same as your body will only absorb what it needs and then turn your wee yellow lol.