It was the drug addictions that really pushed me to consider that there was something different about my experience.

Yes! I've read that autistic and ADHD people are more likely to self-medicate using drugs. For me, alcohol was amazing. It would dull my senses and slow my brain down enough to be able to focus on the immediate world around me and focus. I'm happy that you took that experience as a learning moment to figure things out. The way I see it, we're not drug abusers. We're trying to cope in a world that is not considerate of our needs and then blames us for the difficulties we have. It can be pretty alienating. In the words of my favorite English musician, "I've always felt so fucking detached, and broken, bruised, and mismatched. Find it hard to relax. Living under the cracks. Trying to fill in the gaps. Lying here on my back. Still, I can't find a sense of peace in my mind, declined it. Pulse increased and my sweat combines with a feeling so deep I fall inside it." The song is Depression by Ren.

That’s what finally convinced me but I didn’t seek a formal diagnosis, there’s no point now. Maybe it’s not even autism, that would be a good one.

If you have doubt, then it might be worth it to clear it up and potentially access relevant services. Otherwise, if you don't already, you can try applying techniques that help autistic people and see if that makes significant improvements in your life.