"Who am I?" has no answer to it; it is unanswerable. Your mind will supply many answers. Your mind will say, "You are the essence of life. You are the eternal soul. You are divine," and so on and so forth. All those answers have to be rejected: NETI NETI - one has to go on saying, "Neither this nor that."
When you have denied all the possible answers that the mind can supply and devise, when the question remains absolutely unanswerable, a miracle happens: suddenly the question also disappears. When all the answers have been rejected, the question has no props, no supports inside to stand on any more. It simply flops, it collapses, it disappears.
When the question also has disappeared, then you know. But that knowing is not an answer: it is an existential experience.