sons behaviour after seperation

[Mummyoftwo91]

Already posted this in a different area but here seems better, My husband left us about a month ago now and my 4 1/2 year old has not taken it well at all. His behaviour has been horrendous he's very angry and lasting out and spends most the day screaming or whining about anything and everything. He has been pushing his little sister around and just not being very nice, he keeps drawing pictures of our family without his dad in and says he thinks daddy doesn't love him anymore. I've spoke to his school they are trying to help him understand and reading him books ect and I've told my husband but I'm just mentally drained from him every day, I know this isn't his fault I just feel so sorry for him I don't know what to do to help