Thank you so, so much for sharing your story on here. It's a really brave step to take opening yourself up like this. Just making the first step is really huge and you should be really proud. Not only will it hopefully help you get to a better place yourself, but it can really help others, who may be going through similar things.
From your post it doesn't seem like you're a bad communicator at all. You've shared your situation with openness and authenticity. Openness and authenticity is what the world desperately needs more of. You can really help others by being open and authentic in this way. I imagine most rehab services would include peer-support groups, and I suspect you would have a huge positive impact on such a group.
I attended peer-support groups for anxiety and depression for many years, and found them very helpful. It was very scary and embarassing for me at first, as I felt extremely badly about myself at the time. I think the support groups were so helpful for me because everyone attending had experienced bad anxiety or depression, and so there was this sort of intuitive understanding among the group of these issues: this meant people would very quickly understand what the current speaker meant, and could relate to it on a gut level. This created a strong sense of shared empathy that made me realise I wasn't at all alone with these issues. The groups also helped me realise that problems like anxiety, depression and addiction are shared by all kinds of people from all kinds of social groups and backgrounds, and that the super negative view of myself I had developed wasn't necessarily true. Hopefully these forums will provide something similar for you, and help you build confidence for the in-person groups you might encounter at rehab.
There are also 1 on 1 phone counselling services available from Beyond Blue (1300 22 4636), and Lifeline (13 11 14) if you have major crisis moments. If you're a guy, there's also Mensline (1300 78 99 78). I've called all these services multiple times in the past and found them helpful.
Another good first step is talking to your GP. Do you have a regular Dr. you trust to talk to about anxiety and addiction with? A GP can set up what are called "mental health care plans", which allow you to see a participating psychologist or social worker of your choice up to 20 times a year for free.
Anyway congrats again on taking the step of posting on here. It's a really gutsy thing to do and you should be proud.