How do you get through the mum guilt?

Kim • Mummy to Aliza, 09/06/2017 - Henry 05/02/2020

I have a 2 year old daughter who turns 3 next month and I have a 3 month old son. I feel so guilty and I get upset every night because I can't interact with my daughter as much, I feel like I am always saying no, she will ask me to play this and that but most of the time it is when I am feeding my son, I just feel like such a horrible mum at the moment, plus her behaviour is getting a lot worse and I feel like it's my fault because I am not giving her as much attention. I really am trying but I can't help feeling such a rubbish mum, I have no one to talk too. I just feel like such a failure. Anybody else been through the same?