Shoulder to Cry On

I've been having trouble with my son. He started kindergarten this year, and just hasn't been handling it very well. He absolutely knows better than to yell at his teacher, or hit his teacher. He knows it's wrong to push other kids and make fire truck noises during class. He knows there are consequences for his actions, but it doesn't seem to faze him. I'm at my whit's end, and feel like the worst mother in the world because of his behavior. I cringe every time the phone rings, praying it's not the school calling again. My family is supportive, but unhelpful. They've never had to deal with this before, and honestly, it's not their burden to carry. It's mine, and mine alone. So, I'm sending my woes and fears out to all of you. Not expecting help, just needing to voice my concerns, instead of keeping it inside all the time.