Why do I hear voices when I'm high?

I hear voices when I'm high. I always have, but it's getting more frequent and more distinct. I was letting the dog back in and said "come here." I heard what sounded like a crazy, older woman. She said, "Yes, come here." It was sort of backing me up, mocking me, and talking to me at the same time. She kept saying "come here" every once in a while until I went back in the house and locked the doors. I also hear people yelling for me. I have had that my entire life, though, not just when high. About people yelling or speaking my name, that is. And it feels so real, that I get up and ask if anyone yelled for me. It's usually when no one is even home. Is there a reason for hearing voices? It happens other times, too, but it's hard to remember what all was said. They're full, understandable sentences, though, all of the time. Help?