Yes, I do think stress is a factor in the weight issue. I have a stressful job and I feel a lot of anxiety at work on a regular basis. At 5'2 and 104 lbs I am not technically underweight but I am at the very bottom of my healthy weight range. I would love to get up to 110. I am hoping that addressing all of these issues will also help my anxiety which I believe will help me to gain weight. I enjoy eating very much but when I feel anxious my appetite disappears.
I will certainly look into all of those supplements you mentioned. The only thing I take now are probiotics and omega 3's.
I agree about digestion and health. I am just glad I found all this info now instead of ten years from now.