I think my 5 year old is autistic

I think my 5 year old is autistic. He is very sensory, we have struggles with socks, shoes, labels etc...He doesn't take too well to changes in routines and I struggle to get him to school some mornings if he knows something is going to be different there.

I have spoken to my husband about it and he has eventually agreed with me, it took a while as he didn't want to admit it, however whenever I mention things to him he tells me to stop saying it could be autistic....I have explained to him that I'm just trying to build a picture.

I've spoken to the school and they agree that there is 'something' and are supporting me with an autism assessment. I do feel he masks it at school and he goes into himself.

I haven't spoken to the GP yet as was going to do a self referral. Have others gone this route?

I just want to know how to better support my son.