I know exactly how you feel. In the majority of my social interactions I worry about how other people see me and this leads me to monitor my behaviour which in turn makes things more anxious and tense for both me and whoever Im talking to. It can kind of becomes a viscious cycle yknow? But if I have any advice, instead of looking at yourself through their eyes think about how understanding they'd likely be if they knew how much distress it caused you to feel the way you do. Instead of assuming that they think youre a creep for your quiet demeanor, assume theyre wondering whats wrong and why you arent the same person they remember hanging out with. Above all else remember everything will be okay regardless of what other people see in you.