Daystar, it sound like you experienced "Atman", the totality of the world as known subjectively (but seemingly objectively).
One line of thought might suggest I met my Holy Guardian Angel, or Inner Self, or True Self. Perhaps it was nothing like that. The entity did seem to be part of me, but also very distinctly not-me.
Just because the being did not seem like you, it does not rule out the possibility that it is you. The reason being is because "you" (or the Self) is seperate from, the body, the ego and the mind. Once we realise that we are neither our bodies, nor our ego, nor even our mind, we realise that we are the Atman: the still, permanent and silent witness that underlies all the fluctuations of the mind, body and ego. It is said to have never been born and will never die. True liberation is said to come from a realisation that that which really matters can never be hurt or damaged. The phrase "Tat twam asi" means "you are that" and means that the divisions between Self and All are merely an illusion. It is this realisation which is a beginning of "liberation".
An exercise to try to capture the "Atman" is to sit still, remove all senory input as well as thoughts and try to "think" of one spot. Diminish the spot in your mind and try to see the observer who is observing the spot. It is tremendously difficult, if not impossible for the vast majority to observe the observer without an object that it is observing. The observer is only percieved by its reaction to other things. Without other things, it itself is unobservable for many. Philosophers argue til they are blue in the face about whether the Atman is a being in itself or whether it is only produced by the presence of the Other.
In Hinduism the Atman is the essence of All, but in different branches of Buddhism it is at the Source of all ignorance which is the Cause of all misery. The realisation that only the Atman matters can sometimes be compared to the state of Nirvana.
I hope that was clear enough, these subjects tend to have an inbuilt vagueness to them, lol. I don't know if you've already looked at the Buddhist or Vedanta (Hindu) conceptions of the Atman, but you may find some parallells there.
If this had happened to me, i would shy away from the appellation "God" because of my disdain of the Judeo-Christian and Islamic concepts. However, i'm sure some of the other concepts are just as wacky and bizarre.