Hello, I have arrived from Ireland back to India after an year. And all of a sudden I am facing discomfort in stomach since a month. Now everything seems to have worked out by itself as I was diagnosed with gas. Since then I've been working out extremely hard, have not taken liquor or smoke. However, almost every time I see that the stool is black and this had got me worried if I'm doing something wrong. I take a multivitamin supplement everyday and whey protein. Please advice me in this issue. Thanks in advance