If time is a dimension and we are able to travel both backward and forward on it, then you are technically always everything you ever will or have been.
Travelling back in time does not re-create the past, that is impossible, instead it must visit dimensional locations that are currently in existence. Time travel is our way of accessing these dimensional locations, without a mode of time travel we have no access to them. Consider an analogy to movement: We move in the space dimension, a mountain exists in this dimension, we cannot access this mountain without a method of locomotion within the space dimension, like our legs. We currently have no methods of locomotion backwards in the time dimension. We have a natural tendency to move forward in this dimension, and we can speed up how quickly we move forward through this dimension, but we have not figured out how to move backward.
If you were to somehow move backward in time and find yourself at a younger age, that means that there is a different physical copy of you in another location in this dimension. Theoretically, if you were able to reduce time to its smallest unit, then there should be as many of you as there are single time units in your life span. So there are many yous all reaching back to your conception. This leaves us with one problem: are these yous all considered to be the same being or is there a separate being for every time unit in your entire existence? If all the yous are to be considered the same as one you, then you are technically your entire life in one instance. You are a baby, adult, geriatric, all simultaneously. You are yesterday, today, and tomorrow. If all the yous are separate and individual beings, than all you are is this moment. You are one unit of time, and you have become several new beings while reading this.