Cancer or Hemorrhoids?

So yesterday I had diarrhea and a upset stomach. I pooped about 4-5 times. The first 4 were normal looking. So the 5th time, Blood came out, bright red blood. I took 2 doses of pepto bismol. Now today I pooped again, and it was really dark green, and i noticed red bright blood again. But then I went again, and no blood came out, and it was just dark green. What could be wrong?