Fasting, schizophrenic and take medications

I want to fast to reset my body so it will be easier for me to stay on a salt, oil and Sugar free whole plant based diet, and to give up caffeine and artificial sweeteners.

I do need to lose weight but my main objective is to get my health back. I think years of drinking diet cokes has ruined my eyes, I have vision problems so bad, one eye is off, and they are getting glossy looking. Veins have recently begun to show on my legs which is new and a bad sign that my body must be struggling.

Problem is that I am schizophrenic and take anti psychotics. I can't go off those because every time I have in the past, I get psychosis. I come from a family full of schizophrenia so I am sure it's genetic and not just specific to bad diet, even though, I'm sure getting my health in order will help make it less severe.

I am starting my fast after thanksgiving, cause family won't understand, no getting out of that.

Not sure how long, but at least a week and a month if I can make it that far.