Where do I start?

So I'm new here, new to taking steps towards reaching out for support and seeking help. 

First of all I guess I'd better introduce myself, I'm Lydia 27, I have two children. My 9 year old son is the reason I'm here.

When marley was a baby I knew he was autistic, showing traits of autism. Mild? I don't even know what is the correct way of explaining.

When he was in year 2 I took it as far to attempt to have him assessed. I failed, didn't know what I was doing and that time in life was not good. Fast forward a few years he is now 9. I can't just carry on without support and help anymore its becoming hard because I'm doing it wrong. 

What steps do I take? What do I do?

On Monday after school I'm going to speak to his teacher, she's already told me I need to see a gp forest but I want to explain why I am to her, and get the schools support. 

My plan is to start a diary on Monday, a behavioural diary. And I will do this from now until the summer holidays end. I will also write a list of past and present traits, reasons I know he is different. I will then take this with me and see a gp?

This is as far as I've got. And joining this site. 

Help lol x