Are you saying you see your son for 4 weeks at the weekends and then not for 4 weeks because of your shift work? I'm not sure I've read that correctly but if I have this is what I make of it:

I have a similar set up to you, my son (6) acts up very badly at home, he has had therapy to help him as his behavoir became out of control and the therapists conclusion is that his dad is inconsistent with attention on contacts, one week giving him lots the next palming him of on babysitters. So from that experience and that of other single parents in this type of situation I would say that part of the problem with your boy is the lack of consistency with contacts. I know with shift work thats going to be hard to resolve but try to come up with something. He probably does find it difficult with all the other kids to contend with, (I also have 4 others) he'll be attention seeking from his mum to make up for the attention he's not getting from you during periods of no contact. You have a huge amount of power over his happiness in this situation and your attention is more important at this age than you probably think. You don't say what your relationship with his mum is like now but don't get drawn into laying blame on each other as he'll play you both off even more and neither is being a bad parent its mostly down to circumstances, if you get along reasonably well you'd do well to meet up for a coffee now and again to show a united front to him to help combat his story telling.

I have a lot of contact with a lot of single parents and it does seem that its boys this effects, girls seem to handle it much better.

I hope that doesn't sound like I'm laying any blame myself, whereas my ex is just lazy you sound like you really work hard at being a parent but have difficult circumstances to work around.

Hi Sarah.
Many thanks for reading my post and your great reply.
My circumstances are really spot on with what u say.
My relationship with hes mum isnt the best at times but resonable at times for hes sake.
She is engaged to another man now and has a 1yr old like i said in my last post. He gets on with her new man most of the time but plays him too, and says to me that :he hits him: etc....
i work in a factory and my shifts are correct in what u have interputted.
its hard cause i would honestly love to take him every wk or wkends but cant and with the way the world is going; jobs are few and far between. Hes mum says well youll have to try and find a more suitable job, but to be honest i really like my job now. not sayin i put that before my son cause thats what she thinks and constantly says.
its virtually impossible to meet up for coffee with hes mum etc like u stated as its a very far distance between us.
he keeps asking when am i collecting him to hes mum and when she tells him, he goes off on a major tantrum.
it kills me talking to him on the phone with isnt much cause he gets way too upset when he speaks to me
many thanks again Sarah and i hope we chat more or anybody else that has advice or going through the same misshap