At a loss

So we just had our baby via C-section 19 days ago. My husband already went back to work and my oldest two are waking up constantly at night. They are 4 and 2 and my husband looks over at me at night to help and I’m usually nursing when they get up. There has only been one time I’ve been able to help. When they get up they want all the hugs and cuddles so going in there and plopping them back in bed with a newborn on my breast is hard to do. Newborn is not gaining weight so it’s important for me to nurse him every two hours even at night and it seems like that is the same time my other kids are waking up. Prior to baby we had maybe one to two wake ups at most. My husband took care of our kids for the betterment of two weeks and I’m not sure how anything was working but their routine was way off and they got back on their schedule a few days before my husband went back to work. He works a high maintenance job and if he makes a mistake it could be detrimental….how can I get my kiddos back on track? I’ve been so worried about my newborn not gaining weight that nursing has been the most important to me but I also want to help my husband in the process so he’s not dead tired going to work.