What disorder am i? What is this? someone help me?

If you’re worried beyond normal insercurities and discomfort it sounds like you may have body dysmorphia, causing you to have a negative perception of your image. This is actually common as people in the present criticize themselves more than they need to. If you want to lose weight go on an actual diet, as you said you didn’t eat much which in many cases slows down your metabolism because your body isn’t used to digesting more than a fixed amount of food. Once you are on a good diet you’ll eat the proper foods and possibly start out with a bit more than you eat or more health foods at once to get your metabolism to speed up a bit. Also remember that weight and appearance can vary based on how much muscle mass or fat mass a person can have. If you are an average sized person you will weigh more if you have more muscle mass than fat mass because muscles take up less space in your body than fat.
If you go on a diet and exercise plan you’ll definitely lose weight, but a proper diet is essential because you cannot exercise without proper fuel. A good diet will not make someone anorexic, it’s supposed to take out the unhealthiness and replace it with nutrients and proper fuel. On a diet you can lose weight but you may also gain healthy weight from muscle mass.
Going on a diet is your choice, however. You don’t have to do it if you’re worried or trying to please anyone else, do it only if you want to or it’s a necessity.