Dealing with 4yr old difficulties

My son is 4yrs old he will be 5 the middle of this year. He has always been active, very active. He is a beautiful, kind, caring and loving boy. But we have moments, and lately these moments are becoming more and more frequent, he becomes aggressive and without warning, he will hit mainly his older brother without warning or being provoked. He yells, he says inappropriate things (that he has heard at preschool or out at activities) and laughs about it. He throws things... A lot. He breaks things with little to no remorse. He is having accidents everyday. He has been on an elimination diet from 4months old and is still on a moderate elimination diet, he eats well and a lot. He sleeps almost 12-13hrs every night. He plays sport and swims. He is outside a lot and constantly busy. Our concern is these outbursts that he just can't seem to control, the paediatrician gave him blood pressure meads to calm him down but all it did was make him sleepy all if the time and took away his personality. We are consulting a dr and seeing a new paediatrician at the moment. My question is to parents who may have been here before, how do you deal with the outbursts? How do you explain to the older child that we understand it's not the right thing to do and to retaliate only makes things worse and have them understand? There is turrets that runs in the family and the adults that have this often talk about the urges, that they need to do something to relieve the urge. I have spoken to the drs about this but because he is so young there isn't much they can do.
I love him with all of my heart but some days when we have outbursts and accidents I just feel myself falling apart and not coping at all.