Answer:
There is a large list of characteristics associated with Indigo children (see the Indigo characteristics link at the bottom).
Most of these characteristics are worded in such a way that most adolescents are likely to be Indigo children. "Have strong empathy for others or NO empathy", "Find it torture to waiting in lines, lack patience"
Others 'characteristics' don't actually help us identify Indigo children. "Need our support to discover themselves", "Are here to change the world", "Know they belong here until they are told otherwise".
Finally, there has been no sound evidence of the existence of Indigo children. So the most reasonable answer to the question is, "You're not". << Science is a mix between fact and imagintion,just because there is a lack of 'hard fact' doesnt mean that people cant think they are psychic or different, they can believe what they want.So if you still believe after reading this, that you truly show these characteristics, then, for all you know you very well could be an indigo or crystal child:D ( don't believe what anyone says,they have just as much proof as you,never let somone destroy what you believe in)
Though you could look into scientific testing if you have reason to believe that you might be supernatural in some way.
Also, usually some psychic awareness or the other gives them away... :)