I feel awkward in my own body

I feel like I walk weird, talk weird everything I do feels wrong, and I’m constantly worried that everyone knows that and thinks I’m weird. Even doing something like going in a store by myself, I feel like I’m not moving my arms right or I’m not being friendly enough, and people will think I’m mean or slow or something. It’s this awful feeling like I’m doing everything wrong and everyone knows it. This is already a tremendous burden to walk around with but to add insult to injury, I feel like conversationally, I’m terrible. I’m either extremely conservative and quiet or way too expressive and weird. (No one’s ever told me this it’s just that way I feel) I don’t even care if I have friends. I just want to be comfortable in my own skin.I feel like everyone was born with a rulebook embedded in their brains but not me. How do I get better?
(P.S. people have told me they think I’m autistic but I haven’t been diagnosed)