I feel invisible, as if I am watching the world from a screen or a glass wall from which no one can see me, as if there are restrictions that prevent me from sharing anything with the world.
That's a terrible way to feel. You are just as real as anyone else. Try to focus on things you can do ti put yourself out in the world more. There's all kinds of little things you can do to warm up to it. Start a list of things to get you out. Going for regular walks is a good way, get a library card, volunteer for an hour or two a week somewhere. Think about your talents (no matter how small), things that you enjoy doing. Do whatever you can to get yourself moving and outside of your head.
@Fohb460 This does not work, because I cannot always leave the house, but even if I go out and appear to people, I feel the same way with them.