Jean-Paul Sartre didn’t believe human beings have an essence, being some sort of fixed entity, rather our essence or self is something we are constantly striving for. That is why he said “existence precedes essence”, first we start to exist and then we start to make something of ourselves.
Therefore he also said there is no ‘I’, meaning we have no fixed identities, instead of being ourselves we are always becoming ourselves, creating ourselves. I think he was right.
So my advise: don’t ask yourself “Who am I?” Instead, ask yourself: “Who do I want to become?”