Has been deteriorated = passive voice. So you are saying that someone has deteriorated your mental state. However, you can't say that. Deteriorate is something that happens. It is not something that someone does to something. So you cannot use passive voice here.

Almost! Deteriorate means "become progressively worse" so for a grammatically correct sentence you would need to say "my mental state has been deterioratING" OR "my mental state has deteriorated" You're doing great, happy learning :)