Why do i sometimes feel fat even though i'm not?

Perception.: Sadly, in america being thin is prized. Thin people are extensively used a role models (see ffilm, advertising etc). As a result, someone can come to perceive only thin people as being "normal". Our perception of healthy becomes warped. My guess is that you scrutinize your body and weight a little too much. How about aiming for healthy rather than thin? Take care.