My DS6 was also very difficult from 2-5. We joke that he uses his intelligence for evil. Not really, but he's a boundary tester. He still does it, except I've learned to laugh a little about the extremes he will go to to find where the boundaries are. A great example of this was when he was 4 and I was visiting a friend. There was a large fountain nearby and my son managed to dunk his hair in the fountain. I told him to stay off the fountain. He obliged, but then proceeded to keep one foot on the ground and straddled the ledge so he could stick his other foot in the fountain. Technically he was "off the fountain". I can laugh about it now, but so very irritating in the moment. It's hard to discipline a kid like that.
He did used to throw epic tantrums too that would last hours. We saw a family therapist when it got so disruptive that we couldn't enjoy life with him. We couldn't go anywhere and his little sister was getting ignored because he was so out of control. He would explode into hours long screaming its over simple things like asking him to get his shoes on. It was a very scary time. In hindsight, this was likely due to a major change be because his sister went to preschool, so our nanny who'd watched him since he was a baby had left.
I do remember feeling relief at dropping him off at school during this time. You may want to seek some family therapy. I read a ton of books trying to figure out what to do and we had a huge "toolbox" to deal with behavior. The therapist was actually amazed at how well we were able to switch from technique to technique. It wasn't like we weren't doing a good job. The parent-child bond had just gotten broken down and we were in a terrible cycle that needed to be broken.
There were 2 things that worked for us that may or may not work for you. First, the child-led play was a critical one. Just 10 minutes to let him lead you and tell you what to do and you indulge him in tons of positive feedback. It felt very odd to do that, but lots of compliments and letting him be in control for a small amount of time helped. He also received undivided attention in a fun, totally loving way. This helped strengthen the parent/child bond again.
The second was that he was dealing with a lot of anxiety. We knew he was able to think ahead through time in a way that far beyond his age. He would constantly worry about things that were happening months ahead of time. We stopped telling him about big changes because he would get so anxious about it. There are some things that can't be avoided though, like summer break. To combat this, the therapist suggested listening to guided meditation to help him relax. We incorporated it into his bedtime routine and he still listens to it.
I just wanted to share that therapy might be something to consider because a pG kid can be very intense and they can understand things that they aren't emotionally able to handle. Just like school, they sometimes require special handling with behavior too. It doesn't mean you are a bad parent. We learned we are actually really great at it, but we still needed help.
Good luck!
