Not sure where to start?

Hi there.

I'm new to this and find this subject (autism) all very confusing. We've always known our litttle boy (now 6) was different but over the past few days it's been confirmed. His school called us in and they have advised us that they beleive he is displaying autistic behaviour. His behaviour at home can and has been challenging but nothing that we would consider as naughty, just hard work sometimes. We've been told that at shcool he finds some lessons difficult and has left the room and gone off on his own and sat there banging his head on the wall or floor, something he has never done in our presence. This is one on trait he is displaying, he does avoid eye contact and has done for most of his life although if i say to him look into my eyes he does with ease. He's affectionate to us, to friends he knows, to our pet cat. He is (oddly enough) one of the most popular kids in his school, and with all the grown ups that know him. His after school club love him to bits, his teachers love him to bits and do on. He is not naughty at all, in fact, he is an absolute angel and has a heart of gold. All of this has been a shock to us. As i said, we sort of guessed he was different but hearing him displaying the type of behaviour he expresses at school and not at home was a shock. He's also really intelligent and this comes from the school. 

We don't know what to do, where to to etc. The school have given us a letter for his GP, we are takimg him there as soon as we can. We are getting the SENCO at the school involved (who is excellent). We just don't know what to do next?

Right now i feel like a crap dad.