I have tried to uncover sources of possible repressed emotions
In my observations, "trying to uncover... possible repressed emotions" is a common activity that rarely seems to produce tangible results.
What I'm talking about is to stop trying, and instead start paying attention to the random thoughts that make you so damn uncomfortable that you would rather do or think or talk about anything else. They occur all day long - some turn out to be laughable, some are pretty mundane but somehow are interpreted by our subconscious brains as threatening to our emotional well-being (such as obligations and expectations), while others create pressure and self-judgment (relationship issues) and still others are existentially terrifying (mortality and isolation). They often overlap.
Another way to think of repressed emotions is that there is some kind of internal emotional conflict that causes a stress response in our nervous system whenever we randomly think about it - which our primitive brains automatically (usually erroneously) interpret as an immediate life-threatening danger, which causes an immediate cascade of physiological responses. These are collectively referred to as fight/flight/freeze, but also include things like long-term inflammation and unsustainable cortisol levels, plus we get the repression of those random thoughts using distraction techniques (symptoms) until we are no longer consciously aware of them.
It's a vicious cycle and combination of factors that is hard to untangle IF you spend too much time thinking about it. The key is to stop thinking about it so much, and instead, engage in exercises which allow the random thoughts to appear in a safe environment, while you practice acknowledging them and examining them and ultimately accepting them - no matter how mundane they might at first appear. FYI, any thoughts you have of "Dude, THIS isn't important, you don't have to look at it, just move on to the next thing" is a trick of your brain.
The purpose of free-writing exercises is to allow those random thoughts to emerge from their unconscious repressed hiding places, out into the open without any kind of filter or editing getting in the way. These exercises come under the heading of "journaling" but we throw out what we write in these exercises, because we're not trying to keep a journal and we don't need to revisit an issue on paper once we've brought it into consciousness. The best free-writing is actually done so fast that it's illegible, and it ignores spelling, grammar, punctuation, and any form of editing whatsoever. Ink pen on paper is the best medium to discourage editing or worrying about readability. I call it "writing shit down" rather than "journaling". Nicole Sachs calls it JournalSpeak, while Dr. David Hanscom calls it "expressive writing". They both advocate tossing what you write.
it just occurred to me that I have not looked that seriously at my marriage as a source of my repressed rage. Believe it or not, this is true! Also, I am 68 and my GI symptoms started at 65, the same age as when my dad died. So, like you, aging and mortality is a big part of my struggle.
There ya go. Two great topics to explore. To get started, google "free-writing exercises for emotional release". Tons of resources. I like one description of "continuous" writing. No stopping, no going back, no editing. One way to start is to literally ask yourself a question - "how am I feeling right now about ___?" Another way is to make a list of things that are on your mind. Your symptoms will probably head the list, but after that... you just keep going, even if you only write down something like "okay, what irritated me today?" or "what's worrying me right now?" Then start writing about the thing on that list that makes you the most uncomfortable, if you can! If not, keep it for later - don't keep repressing it!
As for the aging trigger, I found that the practice of Existential Psychotherapy is super-simple to understand, and, with its focus on the Four Core Issues, aging is covered by all of them: Freedom, Meaning, Isolation/Abandonment, and of course Mortality. These four issues provide a wealth of opportunities for free-writing exercises. I describe my understanding and use of EP here:
https://www.tmswiki.org/forum/threads/who-all-journaled-in-their-healing-process.24313/#post-126503 although I believe that individual was a lot younger than we are.