I agree with others on the dummy thing...my little boy had a small dummy which I lost one day so had to use one that was for an older baby and he took it so much easier. I tried him on the newborn ones again and he refused it! We use the avent cherry shape for 6 months+ now.
Also I agree with the feeding laying down to get yourself some more rest. Does your Ds nap still? If he does take bub into bed while he's asleep and take a nap. Is there anybody able to take bub for a little while so you can go for a nice shower or even just a nap?
I'm still trying to get myself used to getting through the day with a baby and toddler. It's even worse when you're sleep deprived. The first few weeks are the hardest so hang in there it will get better! Just try not to expect too much of yourself in these first few weeks, If you need a break and somebody is there to help take it.
Sorry you are having a rough time
Congratulations on bub I didnt even know you had her! Ive been out of the loop lol