Need help!!

I have a 6 years old son and A month old baby girl. And my son has been acting up for the last couple weeks and it's getting to point where I can't handle it anymore, I tried taking away his game system, time outs, putting him to bed early and not letting him go over to his friends houses. I just feel lost and feel like I'm not doing my part as a mom! And today he got sent home from school for not listening to his teacher! I just need advice on what should I do or who do I talk to about this with?