Why has my kid started acting out?

I’m looking for some advice. I e been very lucky to have an easy boy baby, toddler. He is turning 6 soon and just started kindergarten. We are having more cry’s, whining, dramatic not listening. He is testing me. I dont yell often. I don’t have to. But I’m losing my shit over here. I have raised my voice more in a week than I have in 6 years. I’m not one of this creative parents naturally but I’m trying. Help please.