Sweety, most of us dream about ourselves and do so fairly frequently. In fact the larger majority if not all our dreams invole ourselves in some form, either directly or as observer. Considering dreams come from our personal subconcious and access our personal memories that makes total sense, right?
It is because you are sad about yourself, consciously or unconsciously.try to know yourself by observing yourself. practice yoga. sit comfortably and observe your breath for sometime. you will feel better.