Hello im new 9 Year old Son Assessment

Hi there, after a lot of discussion my wife and I have finally decided to go and see our GP to see if we can get our son assessed.

The main problem we have always had, when talking to his school etc is that nobody else sees the issues we see, at school he is the modal pupil, popular, sporty kind others even going out of his way to look after younger children (he is year 5) the only issues the school themselves have identified is his constant struggles with handwriting, and a tendency to drift off into his own little space in class.

However at home we have a different child, from the second he gets home from school, it is almost as if it has taken all his energy to keep up appearances at school and we get mr hyde.

He is so easily distracted we can ask him and his brother to get dressed as we are going out, his brother will go off and do it and he has got distracted by something and is doing something else.

He is extremely sporty and active which is mostly a positive for him as it gives him an outlet for all of his energy, but if things dont go well or he feels he didn't do something to the best of his ability he will get extremely distressed floods of tears, if you try and console him he gets angry with you.

At home every bed time is a battle from the second you tell him its time to go to bed, he shouts at you gets angry then when he eventually calms down finds every excuse possible to drag out going to bed from thinking he's seen a spider to suddenly needing to ask you a question etc etc.

If he plays a computer game at home the slightest thing going wrong sends him into a rage, shouting screaming, smashing things hitting himself. 

He doesn't have any problems with speech language, or in social situations (although generally nervous to talk to new people once he gets past that he has no problems making friends)

He has massive issues with fine motor skills, writing seems physically painful for him and eating meals he will often revert to using his hands (again when we are out he will persevere with a knife and fork) 

We really need some help we have tried talking to the school and mentioned it to the GP in the past but as the boy that everyone else sees is so well behaved everyone dismisses our concerns.

Can anyone offer any advise on what we should be saying to our GP tomorrow