Hi Honey,
There are all sorts of reasons for this, sometimes it is called, social phobia. Many transgender suffer from it but is not uncommon among adolescents generally.
One of the issues BTW is for people who spend their time on social media, playing online games and meeting people through that, rather than learning how to relate to people face to face.
It can be overcome and it can take a bit of time.
One way may sound so silly but I will say it - it worked for me!
Try joining a club, a hobby that has nothing to do with online activity.
It can be anything. Making paper planes - sounds nuts, good fun. Acting? Painting? Art? Music groups?
The idea is to get out and slowly see other people - as people.
You will soon realise that most people are lonely as well, and want to meet you, so why not join them!