Struggling with Social Anxiety: Need Help Building Confidence

been having social anxiety since middle school i feel like I can't make friends on my own, either people come up to me or on online. i feel so useless not being able to do it on my own. i wanna learn how to do it but my social anxiety is so bad i can barely say hi to my own friends without worrying about being annoying and ill get sick thinking about it, like physically ill. i had a very bad experience in elementary that still haunts me till this day, many people have said to forget about it but i can't and won't. sorry for the dump but how can i be more social without worrying about stupid things? or maybe something to build my confidence?