Technically, if you don't believe it 100% then it's not a delusion, but an overvalued idea. Whether it is psychosis still or not is a gray area, depending on your pdoc. Personally I don't categorise psychosis as a black or white term, but more of a spectrum because people who have had psychosis before can often have more insight for longer the next time. Also people can have overvalued ideas and hallucinations that they're aware of as not real, and then, either gradually or suddenly, lose insight.

So what I'm saying is that even if it's not a full delusion and psychosis (as total loss of reality), it's still concerning and warrants further treatment and monitoring.

Also, lots of people externalise their problems as a psychological defense eg African tribes who see depression as a demon that needs the whole village to come together to exercise (I'm not referring to people who use this in a stigmatising or abusive way), but the idea is that it's not the person who has the demon's 'fault' or anything defective with them. So maybe your externalising your brain as 'other' and responsible for your current situation can also be viewed psychologically as a way to externalise your suffering and provide an adversary to fight against to get better. Just a thought. It may or may not resonate with you.

Anyway, I'm sorry that you're struggling so much and hope that you can feel better soon

*Willow*