If Mike/Ken has DID then he will have memory loss. I have studied this quite a bit, since I know someone like this. This person is very smart, but can never remember anything. This might be because of the effort the brain has to put in going from personality to personality. Or that the core personality blocks the other personalities from remembering things.
By the way, DID does not necessarily have giant personality changes. They can be subtle, which makes it very difficult to diagnose. I'm not saying Mike/Ken has DID, but just that Tourist was right about Multiple Personality Disorder (not "split personality) having memory loss as one of its symptoms.
Again, the catch is that DID is caused by sexual abuse in childhood. So it is likely the abuse caused the DID, in order to hide the painful memories. Mike, has any professional ever asked you about this possibility?