oh also, you may have to initiate the conversation with questions that are yes no answers. Is someone mean to you? Is there a problem? And make sure he knows that you can help him, and reassure him that you love him, and nothing can change that.
This behavior has started AFTER he started preschool? That may be your answer. When my son first started kindergarten his behavior changed dramatically for awhile. I later found out that it was how the teacher was treating him. He was very energetic and loved to tell stories. The teacher I guess just didn't have the patience to remind him when it was time to tell stories or what. In general it just seemed that the teacher didn't like him, or didn't like me and was taking it out on my son. I'm not sure. But I called her on incidents many times where it was either her fault or actually another child. And I figured his bad behavior at home, was his way of dealing with it because he wasn't able to express how he felt. In 1st grade his behavior at school and home was delightful! But his teacher was very understanding, and took time to help my son with time management and such. My son cried when he realized he wasn't going to have that teacher anymore. Then this past year in 2nd grade...some behavior problems yet again. I found out through talking to him that it was a combination of being picked on by other kids (he is a little nerdy but so am I) and a teacher who is not all that great. I had many personal problems with him over the year that didn't even concern my own child. Sorry long story short. Talk to his preschool teacher....about what is going on there, his behavior there, etc. Perhaps even "sit in" and observe his day there. And talk to him. Try to have him "use his words" to tell you how he feels, and what is wrong. So that you can help him solve the problem. My son and I have a weekly "snuggle time". Where we go in the bedroom and snuggle just him and me...no dad, tv, little brother, and we just talk about anything and everything that he wants. And he feels so much better, and his behavior is always excellent after snuggle time.
Has there been anything significant to change to happen since starting preschool? Anything traumatic? Have you ever had him assessed for ADD? This is what your sons symptoms sound like but I'm not a doctor. It could be something as simple as maybe he doesn't know how to properly release his anger and takes it out on you guys because you're his parents. Has he been getting into fights or altercations at school? What do his teachers say about him? Is he able to sit for extended periods of time doing an activity? Television doesn't count. The reason I'm asking all of these questions is because my 7.5 yr old has ADD AMONGST OTHER HEALTH ISSUES. If you want to, go to the ADHD AND THE ADD FORUMS on here and research them. If you are really concerned about his behavior, take him to your doctor. They'll probably end him to a child psychologist or a child psychiatrist. This doctor will have you fill out a form about your child. They'll evaluate your child by watching him play and probably want the child's teacher to fill out forms as well. I hope this helps you out and you can find the info you want. I truly hope there is nothing wrong with your son. Maybe researching different methods of discipline would work. Have you ever tried a reward system with him and lots of praise? It'll probably work. Ask him if there is anything wrong that he wants to talk about.