I am also an introvert and I remember similar feelings in my late teens, early 20s.
First of all, I would suggest working on acceptance of self. That is – it’s fine to be an introvert and to want to spend time alone….easy enough for me to say, but you need to reach a place where you feel fine about who you naturally are (maybe think of it as a work in progress, and even a little bit of acceptance is good).

Once you are starting to accept yourself, there is that feeling of being more comfortable in your own skin, and then you will start to be more ok with little ‘uncomfortable’ things such as social events. If you notice feelings of anxiety or just that feeling of wanting to get away from everyone and be alone, just notice, observe, and realise they are just feelings, and if you accept yourself as an introvert then you know that these feelings are quite natural and perfectly fine 🙂

Also, don’t worry this ‘problem’ will stay with you forever. I was convinced I would always be alone, however I’m now in my 30s, happily married with 2 children, and have good friends. I don’t have a huge group of friends, but I realise it’s quality rather than quantity that is important.

Remember to be kind to yourself.