If you can’t stop talking about yourself and obsess constantly about the way you look, you could be exhibiting narcissistic tendencies, meaning you're obsessed with yourself, especially your outside appearance.
Scholarly types may know that the word narcissistic is related to the Greek myth of Narcissus, a boy known for his good looks who after angered the gods, fell in love with his reflection in a pool. Narcissus wasted away there, too fascinated with his looks to save his own life. A narcissistic person may suffer a similar fate. The adjective narcissistic describes those who are excessively self-absorbed, especially about their looks.