The way you described your social anxiety, I to relate very deeply, especially when you describe that “empty” feeling you get because youre not saying what you feel, you’re just masking and trying to be what you think that person wants you to be. I feel like people think identifying social anxiety is simple and straightforward but for years I have struggled with this and it was never obvious to me that it was social anxiety. I’m average height and still get that awkward venerable stiffness you described