How to not get insecure when people stare at me?

I have had appearance anxiety for a long time. I grew up in a very critical family, among judgmental relatives who constantly made comments on my appearance. So, as a teenager I was constantly told that I need to be less thinner, I need to undergo a dental surgery to fix my buck teeth, I need to straighten my hair etc etc. It wasn't very different with friends either, I once had a very 'religious' friend tell me that she'll pray everyday so that I can get pretty. Once a classmate took a selfie with me and I pointed out that I looked weird due to the filter (it enlarged my already doe eyes and made my already thin face thinner). She told me that although I am ugly looks aren't everything and I need to focus on the fact that I've a great personality. She wasn't joking by the way.

I always get stared at a lot too. It's just not my imagination, anyone who is out with me notices it. When I was at college, every time we're attending a new class, it's me the teachers would pick to answer the question out of hundreds of people. There's a show going on, they need someone from the audience for help or to crack jokes on? Usually me all the time. Getting stared at has further ruined my confidence. I feel like they're noticing my flaws, laughing inwardly at them.

Yesterday I went for a PhD interview. A lot of people were called together for the autumn sem admission interview. At the waiting room a girl offered me a seat beside her and she was sweet. I was sitting on her right and a guy was sitting on her left. Soon he told me that he was from the same subject as me, so I was talking to him too. After a while the girl got out to attend a call and I was going through my proposal. All of a sudden I realised that the guy was staring at me, I looked at him and he was caught off guard. He got uncomfortable, looked away. I wasn't feeling insecure but that made me very insecure before the interview. Thankfully it didn't affect my answers.

How do I not let such things happen vagain?

How to not get insecure when people stare at me?
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