Ask your doctor for something for the pain, I had to get a lot of stitches and the first couple days were pretty unbearable (I'm a single mom of a now three week old and a 2 year old) so I went to my doctor and got some Tylenol 3s and they really helped. As for remembering to eat, I find it helps to go by the rule eat when baby eats. So every time you breastfeed or give baby a bottle, make sure to drink a glass of any type of fluid, and have something to eat. We lose a lot of fluid after delivery for the next couple weeks so it's very important to keep hydrated or else the headaches won't go away. Once you start to drink more water you'll have an easier time going to the bathroom too so that will help. Sit on a pillow or two whenever you can so that you are more comfortable, and make sure you have a sort of station set up near where you usually sit with all the necessities you will need so you don't have to get up very often. Try and go for walks, the more you walk the more used to the pain you will get and it'll feel better quicker. As for sleep, try putting a soft blanket down as a sheet in the bassinet, your baby just might like a different texture then a regular sheet or blanket. Or you can try swaddling baby in a used tshirt so that she can still smell you when you aren't holding her. Try different lights, if you usually have the lights off and a completely dark room, try have a nightlight, and vice versa. Or try to play some soft music or background noise, like a TV. Ah this probably turned out long and a lot of information so I hope this makes sense and can be of some help. I know how overwhelming it can be to do it on your own. Don't be ashamed to ask for help.
BTW baby #3 is named Emily
First of Congrats!your back might be hurting because of the epi i'm guessing but if so its completely normal. stool softener is a must on my list. when i had my first i got supper constipated ( no one ever told me that would happen) and i mean really really constipated so i learned the hard way just had baby #3 and i made sure to ask my doctor for a stool softener right after i delivered lol. rest as much as u can for your headache. our bodies are trying to go back to normal so hormones and less sleep = a headache ughhh... keep baby nice and tight like a burrito lol babies feel safer like that and sleep better to. good luck hope this helps:)