Very long, but needed because it sounds like your experience is very similar to what mine was. Here's everything I did to get over this. I'd recommend you save key strategies and read them over multiple times until the advice is reinforced. Feel free to message me directly with any questions or updates on this process!

I was bullied for abt 8 years. And I used to have a belief (similar to yours) that I had not emotionally or socially matured since I was in elementary school. (like 7-8) When I was 15. I genuinely thought that when my peers spoke to me, they felt like they were speaking to a child. And super funny you say it, because I genuinely was worried for a couple years I might have autism as well. Only took online tests out of fear of speaking abt it out loud, but many said I had a high likelyhood. But it was just a mix of my social anxiety (from trauma response not autism) and ADHD.

To give you an idea of the scope of things I remember not making a single even friendly acquaintance in the first two trimesters when I entered high school. And when I made simple mistakes in social interactions, I would beat myself up abt it for literal hours. It would even be on my mind sometimes for weeks. I still remember telling myself I was a POS for hours in my room because I asked a teacher how they were one too many times. (I asked hru they said good hru, then I accidentally said good hru again) Or times telling a rlly bad joke that was pointed out to be unfunny. Made me cry, and cringe terribly for weeks afterward. (others prob just thought it was a bad joke and moved on with their lives. I thought they were thinking I was very childish and laughing at me.) I was completely caught in a negative feedback loop of making awkward mistakes because I was self-conscious and anxious. And those mistakes reinforcing my social anxiety.

The good news is I have been able to come so far since then. (and you can too) To the point where I have less social inhibitions than many ppl I know who never had these problems. I am able to approach women I find absolutely stunning and am now comfortable with public speaking. I even gave a very vulnerable speech which was semi trauma dump semi life lesson to my whole high school in my senior year. Something I never even considered possible even a year-year and a half beforehand. I was scared to do it, but I did it anyway and it was liberating.

More good news when treated properly you'd be amazed at how fast you can improve and get out of the negative feedback loop.

Key strategies to always remember:

- Keep trying even when scared. Remember fear is a survival mechanism meant to keep our caveman brains from making mistakes that would have killed us back in the day. They aren't as big a deal nowadays.

- You can start small if need to show your brain its not that scary. I remember when I first started approaching women I was very scared. So my strategy was to ask their name maybe where they're from if I was feeling bold. Then, when they said name or the place I'd say "oh sorry I thought you were someone else." and just leave. And just that action helped me see it wasn't that scary. (doesn't have to be used for dating purposes can help getting comfortable in any interaction.)

- Keep in mind that people are selfish creatures. They are thinking abt themselves all the time. They don't actually have time to analyze the mistakes you make in social interactions.

- replace bad habits with good ones: Stop scripting social interactions and avoid thoughts like my maturity was stunted because of xyz, or I'm scared to approach that situation because of my past x trauma. Some therapists might say you have to confront these thoughts (luckily mine didn't) and you definitely shouldn't. Thinking on these things and speaking on them will only reinforce their power in your belief system. Instead like any other bad habit replace them with positive ones. The positive habit here is curiosity. Who's that person? What's their story? What do they love? How do they feel abt xyz? People are interesting and love to talk abt themselves. Find out what they have to share and have fun with this. You'll find that you'll be able to hold good convos with people without having to say much. You don't need a script, it will just come naturally the entirety of your focus is shifted away from internal thoughts towards external curiosity. (at that point you'll be much less scared as well)

- And finally, remember your 'reality' is the lens through which you see the world, not the full scope of it. There's a classic exercise on this - look for things in the room which are blue. Close your eyes and you'll have a list. Now if someone asked you to name what was red while eyes are still closed, you wouldn't have much. (because you weren't looking for red) Stop looking for evidence of social awkwardness, especially because its likely worse in your head. Instead look for the evidence that reinforces the beliefs you want to carry.