Why do my friends like to make fun of me?

You should have your own principles. Generally, you don't have to worry about jokes, but you should have your own forbidden area and dignity. The so-called dragon has scales, and it will get angry when touched. Have your own lamella, don't be afraid to offend others, let others face you squarely and establish your dignity and image. Since you are sad, show it. Don't let people think you are weak. But don't haggle over every ounce. Generous but principled, never compromise on the issue of principle. As for the degree, you can grasp it yourself. I wish you an early trouble.