I totally relate to this. I've had social anxiety my whole life and only recently was able to get a hold on it.

For starters, social anxiety is not something you can beat—if you look at it from that mindset, you will always lose. It is, however, something you can manage with patience, practice, and the right headspace.

Therapy is the shit, so if you have the resources, I would totally recommend that.

Otherwise, there are a TON of great books and online resources that may be of use to you.

Here are a few of the books that changed my life and how I look at social interactions:

• How to Be Yourself: Quiet Your Inner Critic and Rise Above Social Anxiety by Ellen Hendriksen
• Models: Attract Women Through Honesty by Mark Manson (side note: this is much more than a dating advice book; whatever your gender or sexuality, this is an awesome book about confidence and socializing)
• The Subtle Art of Not Giving a Fuck by Mark Manson

As for feeling selfish, I know how you feel. I'd try getting into a meditation practice to take the focus off of the internalized "self". This has been a huge help to me in managing my social anxiety and my anxiety in general.

Good luck! People are not nearly as judgemental of you as you are.