How can I stop my 3 years old son from being violent with others?

My son is 3 years old. He is in daycare for about 6 months now. It seems to me that since he had started daycare he became very violent towards other children. I have heard from the teachers at least 3 times a week, that he had to spend some time away from the other children, because of his violent behavior.  He is pushing, kicking and punching other children.  I have noticed that he is also violent with us since he started daycare. At home, he screams like a "monster" or he calls himself a monster, if he can't get what he wants.  He used to clean up his toys, used his great manners, and had only very little behavior problems, but ever since he had started daycare, he became a "monster".
He also has problems with sleeping. He wouldn't go to sleep in his own bed. He wants to sleep on the couch or in our bed with daddy, that means I sleep on the couch at least 5 days out of seven.  If I put him in his own bed after his asleep, he would wake up in the middle of the night screaming for mommy or daddy. If daddy gets him, he wants mommy, or if I get him, he wants daddy.
I was told by the daycare supervisor that they have to put me in touch with a behavior management agency, because my son's violence is getting out of hand, and the teachers can't deal with him anymore. The daycare is a well organized, well recommended place, and the teachers are all very nice and well trained. So I don't think that the problem starts there. Daycare is not something new to my son, since he was 3 months old he was in a care of others during the day.  I am a working mother with a very tight schedule. I used to work two jobs, and only had little time for my children.  At the time I tried to schedule my work the way that I can spend some time with my children before their bedtime. But since my son had problems with sleeping, I had quit my second (evening)job.
My husband started his own business last year, and as the business grows he needs my help more and more. Now I work from home, in our home office. Unfortunately this means I work all the time, and I have to rely on my 12 years old daughter's help a lot. But over the weekends our family spend a lot of time quaility time together.
What could cause my son's violent behavior? Why can't he sleep alone? What can I do to stop it?

[Kevin Kennedy, Ph.D.]

Dear Andrea,

It's not a coincidence that your son's behavior changed when he began attending the daycare setting. So you already know the time frame during which the change occurred. This is not to say that his behavior is due to the daycare setting, only that transitions in his life at about that time have been unsettling for him.

It sounds like you and your husband are under a great deal of stress, and that your son is suffering from the influence of this. Your note indicates that you sense you are not devoting sufficient time to your children. We often think that so-called quality time will compensate for inadequate attention on a routine basis. But this is not true. Children, particularly during the early years, need regular attention from their parents to the extent that this is possible. We really can't expect to deprive our children of attention during most days of the week and then make up for this on weekends.

It would make sense to consult a mental health clinician to sort out what is happening and to make plans to remedy the problems. Part of the solution will be found in behavior management, but it sounds like you'll need to address the issue of what is causing your son to feel so stressed and angry.