I am on chemo (multiple myeloma) and the heartburn could be from that. For the last two nights I had only chicken noodle soup and had excruciating heartburn that had me bent double. I also vomited both nights. It doesn't seem to bother me too much during the day and I eat only mild foods but I'm afraid to eat anything at night. I don't know how my problem could be IBS. Any ideas?