Child acting out

Tara • Wife and mother to two boys💙
My son turns 6 next week and I'm currently 34 weeks pregnant. My son has been acting out for the last month month and a half or so and I know it can be a combination of things but i'm seriously going crazy trying to figure out what the cause really is. It could be his age and a new phase he is going through, or behavior he picked up from school, or that he is bored because he is on summer vacation. He goes to a day are all week until 3... Once he is home he doesnt listen and needs to be spoken to constantly. It could be because the baby is coming soon too but i feel like he's a little old to be acting like this before the baby is even here. I really want to enjoy my last few weeks with him as my only child but all I do these days is yell at him and get mad at him. I'm so drained from all of it honestly and i just wish he would snap out of it but it clearly isnt that easy. I really don't know what else to do, i feel like im constantly the mean mom.