I will only give you the facts here, because what you need right now is good, hard, logic. I will address "auditory and visual hallucinations".
First off, it is the most important thing that you remain aware of the fact that what you are experiencing is a creation of your own mind. Hallucinations are internal processes, not external stimuli; what you are "seeing" is not really there, and what you are "hearing" was never spoken. Hallucinations of any kind carry the potential hazard of driving the victim to a psychotic break with reality. So it is paramount that you remind yourself adamantly that your hallucinations are not real.
Hearing voices carries a few causes, some more severe than the rest, and it is generally the best idea to consult a doctor, but in the end, all hallucinations are the result of the brain entering a state similar to sleep/
A high fever can cause you to hear voices if you are dehydrated enough (basically, you are beginning to lose consciousness, and your brain is struggling to enter a restful state to help your body recover, so the fever-hallucination is basically a wakeful dream. Alternatively, a high fever can trigger your brain to release certain endorphins and begin to misfire the hormones responsible for sleep. Again, the brain begins to function as it does during sleep, explaining the hallucinations.
Secondly, a tumor can cause hallucinations, but the chances of that are astronomical, and if you've had a CT scan in the last three months, they'd have seen that; it's VERY specific, so in all likelihood your hallucinations are not the result of a tumor, but you can always go get a CT scan just to be sure, that's your prerogative.
Now, I will explain auditory hallucinations: most auditory hallucinations are the result of the individual becoming aware of their own "subvocalization", which is a universal human phenomenon that is also called "internal monologue". It is considered to literally be the act of thinking, and some scientists think that developing language and writing led to the development of "subvocalization".
Some interesting facts about subvocalization.
You can control it:
Pick any writing nearby, then pick any person you have ever known in your lifetime. Read the writing silently, but in your mind, remember that person's voice and read it in their voice. You will hear the words in your head with the voice of the person you selected!
The Speed-Reading program common to American Public Schools functions in part by teaching the child to read without relying on their subvocalization to narrate to them. Some people find it difficult to read faster than their internal monologue, because as they read it on the page, they hear it in their mind. With practice, you can turn off subvocalization while reading and read faster; hence "speed-reading".
Moving on.
I will provide information on schizophrenia. This disorder is very serious and is not to be ignored. Left untreated, the sufferer loses all touch with reality, it is not pretty.
Schizophrenia is a psychological disorder in which the individual experiences hallucinations and suffers from delusions that are apart from reality. Schizophrenia symptoms are split into two categories, Positive and Negative. (The individual may experience symptoms from both categories).
Positive Symptoms:
While it may seem odd to characterize symptoms of schizophrenia as "positive", these are by no means "good". They are simply the least of the worst. Positive symptoms include a distortion of normal functions.:
Here follows a passage directly from the DSM-IV-TR (2000)
"Delusions are erroneous beliefs that usually involve a misinterpretation
of perceptions or experiences. Their content may include a variety of themes (e.g., persecutory, referential, somatic, religious, or grandiose).
Delusions of Persecution are most common; the person believes he or she is being tormented, followed, tricked, spied on, or ridiculed.
Delusions of Reference are also common; the person believes
that certain gestures, comments, passages from books, newspapers, song lyrics, or other environmental cues are specifically directed at him or her."
Delusions of Control are the belief that something is trying to take control of them, and is characterized by the presence of auditory command hallucinations (voices telling them to commit certain acts).
Delusions of Grandeur are the delusion that the individual is much more important or of a disproportionately higher stature than their reality. (also falls under magical thinking; the person is destined for greatness, is guided by a mysterious force, etc). Finally, the individual exhibits a "word salad", their speech is difficult to follow, jumps from topic-to-topic or is a jumble of inarticulation and run-on speech.
Negative Symptoms of Schizophrenia are characterized by the absence or loss of normal functioning. The individual may not express emotion (called "flattened affect") or may express inappropriate emotions (such as laughing at sad events, or vice-versa). The individual may exhibit comatose behavior, fixing themselves in odd postures for extended periods of time and be unresponsive to external stimuli.
If you have any questions, comments or concerns, my inbox is always open.
