Sounds like really bad pre-occupation with what you'll tell T, etc. and anxiety. I remember when I would have a really intense session with T and would be driving home and drive right by my exit and panic (Where am I? How do I get home? How did I get here?). Everyone dissociates (what happens when you "get into" a really good book and are not aware of time passing and your surroundings or you are driving to work, arrive and don't remember how you got there, etc.) and when you get something that intense going on that has you making mistakes when you don't want to (upsets your "autopilot" even :-) then you need to calm yourself down some; tell yourself that you will not tell your therapist everything all at once but will just discuss X subject/incident this session and not worry about what might/might not happen after that until after that and so on.