I have been having memory problems, difficulties with doing math, etc. for a long time. I even had to give up teaching and go on disability. I finally got permission to have an official test done recently. I came back with a diagnosis of "mild cognitive impairment." My psychiatrist is cutting me down on my Klonopin to see if that will help.
My suspicion: It can be the depression or some other actual disorder's side effects and/or the effects of the drugs you have taken or are taking right now.
Note: I have Bipolar Disorder. Also, I do see a neurologist and at one point I had a brain scan. I have had two mini-strokes, but they weren't in areas affecting cognition.