Tec you must seek medical help, now. Cofty even helped to find the origin of your "voice", you simply can't deny it, it's a fact.
Like others have said, everyone have an internal dialogue with our subconscious. It's not a voice external to you, neither is a voice from a magical being. This internal "voice" was evolved to express the meaning of subtle perceptions that our conscious mind can't easily grab. It was vital in a time where the jungle's law ruled. Today it help us to spot more sophisticated predators like conmen.
{yet you believe man came from monkeys.}
You can't believe in science, in science you must understand and then accept, after that you must keep trying to refute the acceptance. The theory of evolution is under this process since 1850's, and until now it have passed all questions.
If you take "monkey" as a primate, man did not came from monkeys, man IS a kind of monkey.
The homo sapiens belong to the order of primates, same order of all monkeys.
So, we accept we are a kind of primate. And we came from a being similar to a bacteria, we call it LUCA.