Why am i skinny, i dont feel like eating, do i have eating disorder?

There are many forms of eating disorders, from your description of what's going on, it does not sound as though you have an full blown eating disorder at all. I would recommend that you meet with nutritionist or dietitian to help you figure out a meal plan to gain some weight and increase your muscle mass. I would also suggest you see your GP if you feel you are abnormally skinny and are not gaining any weight. You might have a thyroid condition, diabetes or another serious illness that can cause weight loss. These are very serious conditions and can not go without treatment.