This post seriously sounds as if I wrote it... I have PTSD and am diagnosed schizoaffective. My T believes that my psychosis could be from the PTSD but says it doesn't really matter as long as the meds work. It's a matter of treating the symptoms rather than the disorder. Whether it's from schizoaffective or PTSD, if the meds are working, then they are working.
I tend to lean toward the psychosis is from the PTSD myself. Pretty much every psych diagnosis I have could be attributed to traumatic experiences. Even mood disturbances. My mood is contingent on how much stress I am under.