Can schizoaffective make you believe that you have other mental illnesses?

I will have times where I am so sure I have certain mental illness, thinking I have all the symptoms. I will fully believe this for a few months and then suddenly this will stop and Ill wonder how in the hell I ever believed I had the illness as I dont have the symptoms or enough to fit the criteria. Nothing in particular happens that makes me suddenly stop believing. It just happens. Im starting to wonder if its my schizoaffective. Diagnosed a year ago. Depressive type