You can absolutely have ptsd with psychosis. The over diagnosis of PTSD and it's exhibition as a fad has watered down the meaning of PTSD so that non-clinicians no longer associate psychotic breaks with PTSD. It is a common element of PTSD in refugee survivors of civil wars. There are many academic papers on the topic if you are interested.

I have had several PTSD informed psychotic episodes.

Some last only hours, though they can last months. There is no way to know what to expect, except that you should expect that they will end. You can slide into them on a dime, gradually, or over a period of months. I thought my in-laws were trying to poison me for two months of this year. I didn't just snap into that, it was a slow sort of decline.

In my experience, heavy triggers have caused me psychotic episodes. Phone calls from a child hood abuser, when I stopped talking to my parents (I stopped talking to each of them separately so this happened twice) and feared they would come and hunt me down, and a recent mother's day. It really depends on the person as to what constitutes a heavy enough trigger.

It's important to bear in mind two things I think. Psychosis is a spectrum: You are not psychotic or not psychotic. There is everything from harmless but strange delusional thoughts to full blown hallucinations and thinking everyone is out to get you. I have find myself some place on the spectrum for a large part of my recovery, usually closer to the strange delusional but harmless thoughts category.