i have been a "shut in" for almost 5 years. the longer you go without talking to people, the more inside your own head you get. obviously you know this. eventually you feel like an alien. i think one bad conversation or even many many "bad" conversations and awkward moments aren't a reason to think you cant talk with people. we haven't actually forgotten how to speak with people.
its hard to have a conversation period when you've been laying in bed for a week and only just showered. or when all you can think about is being violent to yourself. what do you even talk about? can they tell? do they know how much i hate myself? do they know how scared i am of being honest? you are already entering with a disadvantage because your mind causes you to be so persistently negative.
practice in any way you can. sometimes i go on short walks and try to greet people who pass me. and try to smile. i HATE doing this. it almost seems condescending to suggest but it genuinely makes a difference. i hate forcing myself to smile. i gave up on it for a long time. however...... i have noticed people arent quite so weary of you if you at least grin. ok i dont force a smile. its a grin. either way.
you being uncomfortable makes other people uncomfortable. it sucks but its true. so even if they can tell it is a fake grin, it is subconcious evidence to them that you care, and you are trying to make them more comfortable with your awkwardness. it sounds dumb, but i think it helps. i never understood that about my social anxiety. i always thought to myself, "why dont they like me?", "i didnt do anything wrong, why are they uncomfortable around me?". well.... they are uncomfortable because you are uncomfortable.
your silence is perceived as judgement. when they see you avoid them, they dont assume it is because you are deeply depressed, they think it is because you think you are better than them. even when the reality couldnt be further from the truth. no one is a mind reader and everyone makes assumptions they then assume to be true. its so important to remember. you dont know what they are thinking.. they dont know what you are thinking. no one is waiting to tear you down in the middle of a conversation. if you cant think of anything to say, try to mainly ask questions. plenty of people dont want to talk anyways. they just want you to listen.
im sorry for ranting or if its too much. i havent slept and im getting more energy which means im getting manic. anyways so yeah. my advice is... grinning. sorry i dont have more. im not really in a position to give advice but im so tired of being alone. i hope you can feel better.