There, that's good for you to know! You have decided you are not switching T's.

What can you learn from talking to him more about how much the situation bothers him? Do you hope to convince him to become more regular in his handling of you and your session days/times? Do you hope to become not as bothered by the "unknown" next session day/date/time?

The first you have no control over and could lead to dangerous problems of his saying he'll be more consistent but then not being able to keep to that and you are left in a similar bothered state or his not saying, promising, agreeing to be more consistent and your perceiving that as his putting his personal life and needs above your reasonable therapy needs (that he provide a consistent "frame").

The second reminds me of me and my husband saying I do not have an "I don't know" bucket I "have to" understand, have to see situations clearly, feel things one way or another or I am anxious. Knowing this about myself though has been real helpful because I can use the "whole" to comfort me about the pieces; no one experience is greater than my whole experience. The weight of history, of all your experiences with your T and his trustworthiness and care of you has led you to stick with him. When I become anxious because "this" situation is scary, I can remember other, similar situations in the past that came out okay and have faith that this one will too, all things considered.