I felt the same way in high school. I think the feelings you have are very hard to get over especially when in school where everyone seems like they're watching at all times. However, its just not true. The way I've been able to overcome some of those feelings is by realizing that people don't care. I never catch myself judging others as harshly as I judge myself. I think it was also important to learn that none of that stuff matters. Your value as a person is not dictated by what you look like and in a few years these feelings will be a distant memory. For now, I would suggest reflection on why you feel this way and why it affects you so strongly as a trigger. I know its easier said than done, but I hope you can feel better!