Hi,
I am really very sorry to hear that and I then definitely think that you doc is right. Although you may not feel stressed your body is expressing the stress in the only way it knows how, which is to produce symptoms such as your, like pain.
Have you had an counselling since this?
If all your blood work is negative, then can I suggest that you try alternative therapies such as acupuncture. I think this may really be helpful. They will view you as a whole person and they will be able to treat symptoms of anxiety very well. You may find that following some treatment, your belly may be a lot better.
If you don't like the thought of needles, try Japanese style acupuncture. They use very thin needles that you won't even feel and sometimes use non insertion techniques. They also take pulses a lot and use palpation techniques, especially abdominal diagnosis, so if you don't mind someone prodding you belly a bit, they will be able find exactly where your pain is. This will lead to a diagnosis and some treatment. Normally, any pain is seen as stagnation.
You can find a practitioner by going to the Toyohari site. This is the list of Japanese Acupuncturists. Unfortunately, they are fewer than TCM practitioners. If you click on USA, this will give you a list of recognised practitioners.
I have had this sort of acupuncture and have found the health benefits excellent. I have suffered with sciatica for a number of months and have found it great. Completely gone.
You have nothing to lose by trying and you might be surprised by the results.
Let me know if you decide to do it and let me know how you get on if you do?
Take care
Sarah