How do I make a good first impression before I walk in a room?
My guess here is that other people are not staring at you or judging you. My guess is that you are feeling very self-conscious about yourself for reasons you may not understand. Once you get into the room, watch when someone else walks in. You will find that people also look over to see who is entering the room, just like they did with you. People are simply curious about other people. You mentioned you believe you are attractive. Perhaps the other people in the room also see you as very atractive and prolong their gaze for that reason. Don’t assume that someone looking at you is a negative thing. That sounds like low self-esteem to me.
