Honey hugs...I went through this around 9 months ago when DD2 was born.Firstly it does get better, eventually.

Your DS is acting the same as my DD1. It sounds like he is trying to assert his place in the family. Unfortunately they don't understand that mummy needs to be with baby and nor do they want you to be with bub.

My advice is to stay calm...They know when you are on edge. I used to try and get bub to sleep before I put DD1 to bed, that way I could concentrate on DD1. However the best laid plans hardly ever work!!!! On the nights that bub would not go down I would take her with me for story time. I always explained to DD1 that Mummy was going to read a book to Sara and baby. Once the story was over I would sing a song and get Sara to sing a song to the baby. If bub was calm I would then put her in her basinet or bouncer and give Sara a big kiss and cuddle good night. If Sara played up or got emotional I would explain calmly that it was time to sleep.

Eventually Sara was more accepting that I could not always be there for her but it did take time and many nights I would go to bed feeling like I could not cope.

Goodluck