I had an affair with a man two years ago, my husband found out and wanted details, many of the details I forgot. It was very emotional, painful error of judgement. Is it possible that I have mentally blocked a lot of the "stuff" out. I truly can not remember a lot of details about the affair. My husband thinks I am trying to cover up but I am not.
Yes, it is possible that you have forgotten and it is not wise of your husband to ask. Details will only make him unhappy.
This answer may help you, even though it does not exactly apply to your case.