It is possible to be skinny and not anorexic or over-weight but with an anorexic thought process. Roseleigh is completely right; we can't diagnose you but if you're worried you should do something about it. It's important to remember that in most cases mental illnesses are treatable if you just seek help, so if you're worried about yourself, you should get help. It's better to err on the side of caution in these case.