Good Morning Anneski
What an amazing mother you are to reach out to get some support and to go to the ends of the earth to help your son, you are wonderful.
It is really hard to be a carer, to try to pull someone out of the darkness when they are so confused and so hurt and in pain and really don't know what and how and so many of the questions thrown at them there are no answers for. You are doing everything right in that being there to comfort him, even just to sit with him without speaking, to let him know he is loved and supported is wonderful.
You can also ask him, and you probably have already, what he needs in his times of feeling so down, how can you support him, what would he like you to do? Once again he may not know but at least you are showing him that you considering what he needs and not what you think is best.
Talking to a GP can be overwhelming, if you wanted to try again you could suggest a different GP if you felt like a connection was not there, also you can help your son to get the best from his appointment by maybe suggesting he write down how he is feeling and anything he can as to what is going on for him. You can pass this note to the GP and this will alleviate the awkwardness of starting a conversation as they will do that. This may help him.
I am not sure how he would feel about reaching out to Kids Helpline on 1800 55 1800, the are so skilled at speaking to young adults and to being able to support, I do understand too that talking on the phone is hard for some so maybe even a browse of the website to start with and maybe even a web chat:
https://kidshelpline.com.au/get-help/webchat-counselling
Please try to take some care for you too, this is a very difficult time but you are doing everything right and we are here to support you too. Try to get some fresh air, maybe a walk, maybe even with your son, just to get a change of scenery and some clarity, if that is possible.
I too am a mother and I am just so proud of you for reaching out to do all you can for your child.
Hugs to you Anneski
Sarah