In that enterprise one may realize that differences that make you you and not someone else are very superficial. So, if you want to know yourself look for differences between you and others. They are identical and so don't have that uniqueness that would give them an identity that could then beget the question ''why am I me and not someone else?'' Otherwise you wouldn't be you but someone else. To achieve an indentity, uniqueness if you will, one has to be different enough from the rest. The genus-difference mode of definition comes to mind. Per logic one is a specific person based on difference. What makes a ''person'', if that is what you mean by ''I''?

Why am I me? Why am I not the person next to me? When I die, will I be another person in the past or future? Was I another person before I was born? If so, why am I not everyone? - JohnLocke