I wonder if I am brain damaged????

I have noticed that my mental capabilities are not what they once were. I have trouble thinking of words. I often realize that I don't pick up on nuances of peoples behavior or in conversation. Last night a really weird thing that happened that I can't stop thinking about. Derek purchased a new camera last night at Best Buy. He was playing with his new camera and I went up to bed to read before going to sleep. After reading for about 45 min, I came down and got a beer and went back up to read. Derek was still downstairs when I turned off the light about 11:00 PM and I didn't wake up until 6:00 AM. This morning I said to him, "You should take some pictures of the dogs with your new camera". He looked at me funny and said "I took some pictures of the dogs last night. I brought my camera up to you and showed you the pictures while your were in bed reading. You commented on how Fergus's hair looked so shiny and how I needed to figure out how to get rid of the red eye in the photo of Wiley'". I have absolutely NO recollection of his coming up stairs, of the photos or of me commenting on the photos. I wasn't drunk....this morning I noticed that I had only drank 1/2 of the bottle of beer. What is going on with my brain???? How can I loose chunks of time like that when I feel like I am perfectly cognicent ???? Derek says it is because of the narcotics I am taking. I don't think I am taking a high enough dosage to make me that out of it. I am worried that the chemo and subsequent acute kidney failure may have caused some brain damage. I guess if that is the case there is nothing I can do about it. I think Derek has always admired my mind and now I am sure he thinks his wife's intellect has been changed. I am used to being smart and it is hard to feel kind of stupid all the time. I hope it will get better with time.