Why don’t you talk to the doctor about adding a low dose of medication for a while and try it out. That way you could compare how you feel now and how you feel with the medication - and see the difference and see if you do better.
The issue, I think, is that when a person is delusional (and the delusions are negative) they cause a person a lot of stress. That stress (specifically - the stress hormones), if it goes on for a long time (days or longer) can cause damage to the brain. This is one of the theories on why there is cognitive decline in schizophrenia and psychosis.
The medications help reduce your stress and reduce the delusions - which can help your brain.
See this news:
Gray Matter Loss in Brain Due to Psychotic Episodes / Schizophrenia, Not From Medications
And check out this poll on whether people here in our forums have found medication helpful: