oh man. That's gotta be tough. I would feel that way about telling him too. Can you either schedule another appointment on the 6th, or maybe move the appointment on the 31st? That way you don't feel like you are keeping anything from him, and then if you aren't in the better place by the 6th, you could tell him then, rather than feeling distressed about telling him on the 31st.
(I don't know what your T schedule is like, though, so this may not even be a good suggestion.)