I have bipolar disorder. I know it is different than schizophrenia, but the hell we both experience is similar, and the treatment from others not suffering is the same. If you are an adult, your parents can do little to force you into treatment. If your life is in danger, or you are a danger to others, the State can get involved and keep you for a given time, depending on the state in which you live. You can also be court ordered to treatment, though from what you explain above, it does not sound like you need State intervention at this time. As for vitamins, they are good for you to an extent, but they will not replace your medicines. I know fish oil is the one to seriously consider in addition to medical treatments. Many bipolar individuals are prescribed the same type of medicines as schizophrenics, so I understand the side effects on my own body (gained 30 lbs in one month on Zyprexa and it gave me the shakes). This being said, if you look around long enough you may find the MDS that have good results without too many negative side effects. This is where I am at now. I am on a couple of drugs that work alright (though no where near as good as I would like), and I do not notice any side effects.
If you are still considered a child, you should discuss your treatment options openly with your doctor. You may not be able to escape treatment, but you can put yourself in the driver's seat and control the direction of your treatment. If you do not like a certain drug, or what it does to you, tell the doctor. They should change and adjust. They work for you, not the other way around. If you want alternative options to suppliment your treatment, tell your doctor, they will tell you what is safe, most effective, or at least what won't kill you.
Good luck, to an extent I do feel your pain, and know that you are not alone out there. There are many people in similar situations suffering from mental illness, and having others trying to call the shots. You can look up NAMI and have an advocate in your ordeal, as well as support and knowledge that others are out there.