Im on the HCJ diet where I give myself shots. I eat only 500 calories a day. Ive losted 12 lbs in 13 days. Ever since I started, I have had a little bit of stomach pain in the upper region. Its not severe, just uncomfortable. Ive noticed that I cant take certain antibiotics now, because they make it worse. I had heartburn before diet, but have it alot more now. Im having to chew Tums every 3 to 4 hrs now. Can this be a side effect of the diet? I also have to take Pepto Bismol @ least once a day. It does help my stomach discomfort.. Ive been having regular but loose bowel movements, but feces look almost black, (which I did just read that Pepto Bismol can cause that). Do you have any suggestions to help these problems?