For some people, marijuana can bring about mental disorder in those who are already prone to it. Hearing voices while not high suggest you may have schizophrenia. I don't mean to sound depressing, but it's certainly a possibility. Just to get an idea, if it's schizophrenia, its onset usually comes about when people are late teens, but more commonly early twenties. If you are in the age range 19-25 I would say get checked out by a doctor.. it sounds like a possibility. And there are drugs that have a 2/3 chance of completely repairing/lessening the effects of schizophrenia, so seeing a doctor may be to your advantage.

Best of luck man,

Greg