I know the feeling, i'll try to give you something usefull.
Stay positive, learn social skills, eye contact, how to greet people, fake it till you make it, slowly get out from your comfort zone, never isolate yourself, interact with people, smile... These are just general tips I hope you found these usefull
I can’t agree more with ‘fake it till you make it’. I used to be Really shy, but at some point, maybe in college? I just started pretending to be outgoing, and overtime it came more easily.
The nice thing about being a Jr in high school is that you can try it out now, and in 2 years, leave school and start over - so if you feel embarrassed or have regrets you can pretend like it never happened. I decided in college to try out being a new version of myself, because there was no one there to say I was faking it.
Make small talk with people in your classes about school work, etc. to break the ice and then ask them questions about what they’re into. Make little jokes if you can. Do it again the next time you see them, and then again. If conversation seems natural, keep it up. If not, try someone else until you find someone that seems to click with you, then ask who they hang out with. See if you can join in on their group. Good luck!