'Does who you think of as you really exist' sounds like one of those questions that are too stupid to care about, like how many angels can dance on the head of a pin (which those knucklehead Catholics wasted millions of words and hours and thoughts on). Yet, in a time when culture controls our dress, phrases used, hair style, brand of toothpaste, body type, etc... the question begins to make a bit more sense.
Foucolt, a French philosopher who I won't claim to understand too well, says that the Self that you think of as You, is barely there. He uses the example that if a person were to stand in river of culture, only their fingertips would be above water--just a tiny little bit of the brain that is really, truly, ours. That little bitty pea of space is filled with a relatively few number of templates, running from saint to sadist, etc...
This is why, when I ask if you exist, you might want to ask yourself where you do think independently. As any intellectual knows who follows democratic politics, the masses can be manipulated into thinking whatever the propagandists wish them to. Look at other countries, where people are less media savvy, and they are saying in Pravda that aliens are landing and other yellow journalism. America went through a period like this at the turn of the century. Poe wrote during this period, publishing novels in serial form in newspapers that were taken, by the masses, as the truth. The Voyages of Arthur Gordon Pym is the example I always give.
So, if you do exist, are you a combination of the thoughts that you have been exposed to? If yes, then what thoughts are your culture cramming down your throat. Do you easily go with the flow, making your skin change into whatever color the political season demands?
There is also the sociobiological factor, that a lot of your thoughts about the other sex are merely the echoes of the cries of your genes.
In fact, I think that genes are in control of everything. They are in a war for survival and will do anything, however cruel, to keep moving up into the future. Aliens live in them, and they are using us for eternal life, skipping form generation to generation through our seed.... Oh, wait, no that is a dream I had..... but, our behavior is kind of like that, hard wired in, and we all think the same thoughts, basically, from generation to generation. Hedonism and drugs and such isn't new -- it is older than culture, the first way we were, what culture tries to distant us from, take us to some other word created place where we are not chimps, but near gods.
But only words can take you to such a place, because only in words does such a place exist. Here on earth, we are chimps, barely in control of our base impulses, growling at each other in traffic all day, hating the weak for needing us, etc... all things E.O. Wilson found the apes doing (without a countless number of libraries full of ever changing reasons, mind you.
So, try just believing what can be proven for awhile. There is more than one person can ever know that we already do know... So why not start there when building your own personal Cosmology (which is your world view, or the ethics that ground your behavior; a killer would have one seeing blood, a sex addict would be in one surrounded by fucks, etc.... Everyone's cosmology is slighly different. Even those who claim, like in a church, to share the same cosmology, they really can't. Environment and genes and education, etc... shape this cosmology.
That cosmology is the you that feels like you when you think of you. It is also the ape that takes over when you lose control and have to save face to keep your place in the tribe (though it seems like you are just yelling at the dog at the time, or being snide with your partner).
So, do you exist? Or are you just a puzzle of pieces put together by your time?