I have an uncannily similar physical and symptomatic profile. Do you experience anxiety? My symptoms were so intense and unpredictable that I developed anxiety from it. I had to learn to manage and distinguish both issues, which helped a ton. I never had any formal diagnostic as every doc basically says "everything's normal", but I now suspect a heightened stomach sensibility due to multiple COVID-19 infections coupled with a highly stressful period in my life. I haven't had COVID in a while now and my stress levels are much lower so symptoms are mostly gone.
I understand how debilitating and hellish it can be. I wish you all the best!