Hi, I Have Lower Stomach Pain Which May Occur After

Hi, I have lower stomach pain which may occur after eating or not eating at all. I have lost weight. I quit taking my iron tablet, magnesium tablet and it cleared up for a day and now has started back again. I have found that I can't eat or drink anything chocolate or milk products. I do have false teeth which need to be relined and sized would this be causing some of the eating problems. This has been going on for some time and I have had a EG an Colonscopy. Can you help me. This is for my mother who is 82 years old.