Help! My 4 year old is out of control

My 4 year old son is litterly  out of control. My fiancee & I have been together ever since he was about 1...before that I was a single mother, as his father left when he was 3 months old. My son does not have anything to do with his biological father and my fiancee has been more of a father to him than his real dad. My fiancee lost his job and stayed at home with him on days that I worked,  he however has found a full time well paying job and I quit my job to stay at home. My fiancee has control over him he will listen to him and respects him, but does not respect me. He treats me like what I say is a joke. We also have a 1 year old who he treats bad. He kicks him, slaps him, pushes him over when he walks by him, does not share toys. I have tried everything I know to do. Consistant time outs, taking toys away from him. He will not stay in time out, he yells at me and his little brother. I can't take him anywhere by myself in public because 9 times out of 10 I have to leave the store or whatever we are doing because he acts out. I spank him when he gets really out of control and it does not phase him at all. I am at a loss, I don't know what to do. It is a different story when my fiancee is around. He listens to me, does not treat his brother bad, he acts like a normal child. I am starting to wonder if he is bi-polar or something. I can honestly say that his biological father was abusive and had mental problems. Please help!

[kaylagween]

he is probably acting this way because, the change of you vs dad being with him during the day.  for a child it takes a lot of time to get used to a change like this.

some things that can help are following a schedule, not particular a time schedule (just do thing in the same order regular)

find more to keep him busy games, small legos.

also talk to dad about what they did during the day, what their schedule consisted of. so you can see if it is a big difference from now.

(maybe they did something, say at lunch.  and it was the same thing everyday.  he might miss little things like that)

also positive reinforcement is great