Repeating what just said to someone

I've had this habit since I was a child. I repeat a whole conversation or parts of it in my mind right after the conversation is over. I even repeat a thought that comes to my mind sometimes.

example conversation:
-how was the exam?
-I think I did a good job. how about u?
-it was ok. I missed some questions.
etc

5 minutes after the conversation is over (in my head):
(-I think I did a good job. how about u?
-it was ok. I missed some questions.) *repeating x times*

this lasts 5 to 10 minutes max.

is this normal?