Hi Jennie,
I have just posted with a similar story to yourself. My husband has been an alcoholic for over 5 years. When I first suggested he saw a GP he was adamant he didn’t have a problem.
As time went on, he admitted to struggling. Going to the GP for the first time was on his terms and when he was ready. I understand how hard it is to want to help someone you love but as I have learnt, you can’t force anyone in to something they are not ready for.
Could he be shouting at you/telling you to shut up because he knows you are right but he is frightened about the future too? My husband is always very matter of fact/polite about his illness to his family but breaks down when he speaks about it with me. I think this is because we are the closest to them.
I don’t have much advice as I don’t know myself but I can say that your son knows how much you care about him. I wouldn’t give up on the doctors but maybe your son is embarrassed about his drinking and that’s why he is acting defensively when you asked him about it.
Could you look into some counsellors in your local area or recovery groups? My husband did not respond well to AA but goes to SMART recovery.