I understand about the regrets with your father's death. I have lost my father and two brothers. It seems to me, no matter how much we attended--or not--to our passed loved ones, that the regret will linger. Maybe it harkens back to our childhood thinking that we are "responsible" for everything around us, and so we sort of blame ourselves unconsciously for the loss. Then we find particular failings in our interactions to hang this feeling on...
The questions, in my view you might (or I might) inquire about: If I have regret, do I have sadness? Is the regret covering over direct contact with sadness? (In other words, regret to me has a sense of "should have" which invokes a sort of fantasy that involves doing, even in the past. Doing, or believing there is something to be done is a distraction from just the rank, devastating experience of the sadness of loss.) How much of the regret is a sense of hopelessness about the past and how much is Inner Critic making me feel wrong about my past actions? If my Inner Critic is constantly beating me up, what is the effect of this? If I feel responsible for how others suffered, what is the effect on me? On different parts of me?
I think some people seem to find the "exact thing" that emotionally or stress-wise kicked of their TMS. Others, like me just see the whole egoic hell realms of pressure, Inner Critic activity, hurt and sad parts of myself---the whole list is plenty enough for me to see and feel that I would want to--and do--repress and suppress awareness of these painful feelings and conflicts. Right there I have the cause for TMS and symptoms, and then therefore I can treat TMS.
I am glad you are getting counseling. In my opinion, anything that surfaces that connects to Dr. Sarno's work is evidence to start applying to your cure. Good luck in this, and I hope you stay the course and don't give up, regardless of symptoms.