I wonder if what you are speaking of is Gastroparesis. Your description "food lies like lead on my stomach" sounds just like this problem. This problem is not related to cancer (it does occur in those with diabetes at a higher rate than the general population, but you do not have to have diabetes to have this condition) There are medications that help this problem.
You can read about it here: http://www.mayoclinic.com/health/gastroparesis/DS00612
I know of a research study, too that is trying a new medication for this issue, but unfortunately the age limit is 80. But, it is good to know that there are new medications in the "pipe line."
You can mention this to your doctor. Typically a gastroenterologist is the one that knows the most about this condition. You may want to see a gastroenterologist, or ask your doctor for a referral to one.
Please reply to this post if you have any more questions about this.
I am standing by....in case you do.