There are a lot of stories about the Buddha and what he purportedly said. One is in reference to the many public debates as to whether there is or is not a 'self'.'
The story goes that he was confronted in the street by someone who repeatedly asked him this question. He finally responded like this: "I won't say there is a self and I won't say there isn't a self. I will say that I can't find one."
Check out some of the blogs written by philosophers and dedicated students on this topic of 'not self' and you'll see some real hand to hand combat. Very strong opinions and not a lot equanimity.
To grasp this challenging principle and to sense who and what you truly are, I think we need to turn to the practices themselves. They can guide us not to the concept, but to an intuitive understanding.
This talk dives into a few ways to consider this principle that can be so confusing.
One of the "Three Characteristics of Reality," the principle of "not self," can be confusing. You can probably sense, though, on an intuitive level, who or what you are in the absence of 'I' and 'mine.' This talk explores this principle through stories and direct experiences, including a meditation on what are referred to as the "five aggregates.'
Whoever you are, I hope you might find it helpful.