A lot of people really do struggle with accepting the idea that they might have a problem, I think something that will benefit both of you is if you try and empathise with that 😕 I know YOU can see that getting help would be best for him, but he might be resenting or denying that he even has a problem right now.
I'm really young, so my advice probably won't be so helpful to you, but as someone who suffers from anxiety, I would say that if bringing it up is a sensitive subject at the moment, then maybe leave it for a little while. If it gets significantly worse, calmly voice your feelings again. OR, if he seems to be feeling a little better, try talking to him then. He might feel more able to cope. If you have no luck with either of these, try talking to a counselor about his problems, and about your difficulty communicating with him. They will give you some good advice.
Until that point, just let him know that you are there for him if he needs to talk or vent. Don't try and calm him down or cheer him up, BUT do try and create a relaxed and pleasant atmosphere for him when you can. Do nice things for him, even if it's small things, and maybe spend some time with just the two of you to wind down a bit. He will appreciate it maybe even more than he initially realises.
Good luck, and remember, don't blame yourself for any of this, and try not to let his stress make you feel stressed. There are always people to talk to if you feel it's all getting too much x
