CAN I TAKE A MOMENT TO VENT?

My sweet little boy is 3 1/2. He is quiet and shy, but what most of you don't know is he is extremely stubborn. Poor guy got that from both Clark and I I'm afraid. Anyway, last September he started attending preschool and about a month in we started getting e-mails from his teacher saying they were having some behavioral problems. Like, he wouldn't participate in anything they did. Clean up time, he either wouldn't or would clean up then throw the toys and make a mess. Around Christmas time they said his behavior was starting to improve. And I was so relieved. But, that didn't last long at all. So, his teacher and I have been writing back and forth trying new things to help him and nothing is working. Part of me wants to just brush it off because, he is only 3. But on the other hand, She makes it feel like Nick is the only one with this issue. I am getting quite discouraged. Am I not parenting right? Am I not teaching him right? I feel like a terrible Mother. This teacher, I feel bad for her, Nick can be a HUGE handful. He always throws fits, like for anything. Getting dressed, potty time, putting a jacket on to go outside, eating anything, bedtime, playtime, cleanup time, anything. But the other day she wrote and said they had to discipline him because they asked him to sit with his feel off the chair... Now is that really such a thing to discipline him over? IDK I am just very frustrated. And he doesn't listen or obey. Ever. I have even watched the stupid Super Nanny show, and nothing works. I am half tempted to pull him out just so I don't get emails every week telling me how to parent my child. Anyway, I am done with 3. I don't know how much more I can take.