Does my 4 year old have autism?

My son has been showing some signs of autism for around 2 years now. Teachers have mentioned it to me but they won’t test him until he is 6. Recently it’s been getting tougher to understand whether his behaviour is just because of his age or whether it is down to autism. With him not being able to be tested until he is 6, is there anything I can do to get any help in figuring this out?