just for dads helping each other

In the last six months a lot changed, we moved to a new house, my wife had a baby (girl) and my son turned 4 and started school.

I'm not really sure if this is the reason but for the last month or so, my son has more and more temper tantrums. Basically any time we tell him no, he gets very frustrated and angry. Sometimes shouting or pushing me. It's pretty new behavior and I really don't like it. I have talked to him after the tantrums and he usually agrees he shouldn't behave like this, but so far it keeps coming back. One other thing he does is just ignoring us whenever we ask him something he doesn't want to do, pretending he can't hear us.

The last thing I want to do is be angry or use threads (like I'm counting to 3). But sometimes it's the only way to get him to do something (like getting dressed for school).

I would really want to have a better way to communicate without the negativity.