Help!! Changes after baby

Omg I am having such a hard time with my 5 yr old after baby was born (she is almost 4 weeks). You would think my daughter would be adjusted by now. But no she cries every time we put her to bed. She literally falls asleep crying! Then for school she cried the whole first week but now going on her fourth week she has been better but I can tell she is miserable! She is not the same kid she used to be she was happy loud and kind and now she's so grumpy angry tired and hardly likes to eat! I'm so concerned! I know its a lot of changes from the baby being born to going to kindergarten full time and her not being the center of attention. Its very hard to juggle both girls my time isn't enough! Idk what to do can anyone offer advice please!! I want my old happy kid back I miss her and I feel like I'm failing as a mother !