I haven't really felt depressed since I have been on wellbutrin, ...

I haven't really felt depressed since I have been on wellbutrin, but something that is very bothersome to me is that I can't concentrate or remember things the way I used to. I also have troubles getting myself motivated to do something or finishing a task. I can't remember songs that I made up on the guitar, even an hour later sometimes. I'm only on 150 mg once a day, which is better than the 300 mg I used to be at, but still I can tell it is affecting me.