I have posted before about DS1's behaviour, asking for advice on how to deal with it. The first time was when he was 4 and I got some really helpful posts telling me that if I hadn't sorted his behaviour by four I never would 
He has always been challenging in comparison to other children. He is very lively, but also gets very tired. He cannot seem to stop messing about or fiddling with things. I usually can't leave him alone with DS2(4) and DD(3) without there being shouting and screaming as he either takes toys from them or pushes them or bosses them about within a few minutes. He won't stop when asked and the naughty step and sticker charts don't always work as punishment/reward. He behaves better at school, but his teacher has to keep a very close eye on him. I have asked his key workers at nursery and teachers at school what they think and they have always said that he is "at the lively end of normal". He behaves very well in one-to-one situations with me and other adults. With his brother and sister it all quickly degenerates and I find it hard to not become the shouty mum that I hate being. He is also not happy - he doesn't sleep well, says that he has nightmares, and tells me that he can't help doing naughty things because he can't stop the bad thoughts . I try to make him see how much we love him, and that we just don't love his bad behaviour - and he seems to feel secure and tells us that he loves us (he's very cuddly).
I have been on parenting courses and we have even tried homeopathy and cranial osteopathy, having had both recommended by friends. Nothing worked. Finally, his latest teacher suggested fish oils. We'd used a multi-vitamin with fish oils before, but changed to Eye-Q. Within a couple of days, and for the next 3 months it has been like having a different child - he's not perfect, of course, but I felt that we could finally have a normal, happy family life - and best of all, he was happier too. His teacher noticed the difference. Then, last week, it all reverted to how it was before. He had started a couple of extra activities in the week, and I wondered whether they had tipped him over the edge. He only did one of them this week, but it has not improved.
Sorry that this has been such a long post - just have no idea what to try next. Any advice will be very gratefully received.