I also agree with vangogh89. Schizophrenia is usually diagnosed around ages 15 - 30, and it usually shows up earlier in guys than girls. Schizophrenia rarely develops outside those age boundaries. Also, keep in mind that although inside voices are a symptom of schizophrenia, many NORMAL people will talk to themselves too (ie. think aloud, or hear their own thoughts in their head). In order to be schizophrenic, many (if not all) of the symptoms must be present, or one of the symptoms must be EXTREMELY SEVERE (ie. do the voices turn off when you forget about them?)
However, if it's eanough to worry you, you should try to get some help, because it could develop later in life. You could possibly have borderline personality disorder, which can turn into schizophrenia if it keeps getting worse (borderline personality disorder is characterized by things like emotional instability and sudden impulses that leave you feeling empty afterwards). I'm no psychologist mind you, so I'm not diagnosing you or anything
Schizophrenia can hit you hard if you're not prepared. It develops most easily during extremely stressful times of your life. This happened to me last year. In the matter of two weeks, my life was turned upside down. I lost my job, lost my girlfriend, and found out I was moving all at the same time. The stress ended up making me lose it, and I went into a downward spiral of depression and psychosis. The voices in my head increased in intensity tenfold, I saw halucinations, recluded from society, lost control of my emotions. I even suffered some pretty heavy delusions (I believed that there was a demon in my head tormenting me with the voices of all the people I knew and didn't know, and counseling me on how to ease my emotional pain... he told me to cut myself, through nightmares and daydreams, and I listened to him unfortunately. Now I carry the burden of what I did everywhere I go). Eventually, I couldn't take it anymore, for I feared I would take my own life. So I told my mother, and showed her the scars on my hand and arms, and she helped me find a good psychiatrist after going to a couple of counselors. And I eventually got better (and without the aid of pills). I still have some of my symptoms unfortunately, it's very hard to get rid of schizophrenia completely once you develop it. But it doesn't really bother me that much anymore.
So if you're having worries, best to take care of it now and prevent going through what I did (especially if you don't want to make your mother cry...).
One more thing: If you do end up seeing a psychiatrist, and he tells you you're fine, just going through a phase, DON'T get angry at him, feel like he misunderstood you. Take it as a blessing to know you're not going insane. And if it doesn't make you feel better, keep going to the psychiatrist. They're nice people. They're not just there to diagnose problems, they're there to listen and help you organize your thoughts. And don't push away your close friends either. They're good listeners too.
And think happy thoughts...
that piece of advice got me through a lot of stuff.
If you have anymore questions, feel free to e-mail me.