first breakdown

I'm literally at my wits end..my toddler doesn't want to sleep at night she will fight her sleep and stay up till 4-6 in the morning I've tried no naps early maps later naps..she won't sleep I've been suggested to give her melitonin but I really don't want to do that..I had my second baby 3 weeks ago Idk if that's why she is doing this..she's always been a night owl she would stay up till midnight wake up at 10 nap at 1but recently it's been a battle to get her to bed she's on a routine has been since she was born but that's gone out the window I have no help I'm exhausted.. now on to my newborn she's ebf but acts as if she's always hungry but I know she's not she has now spit up on my twice this evening once was a lot it was ever where on her, my bed, and me second time was only a little but I feel like she's overfeeding I've tried a binky and she will not take it at all she will scream till I nurse her..I'm scared she's going to spit up while I'm sleeping and choke I need some kind of advice so I don't go crazy lol