Blood in stool after using Creatine why?

I have recently started using a supplement called force factor for body building. The product is suppose to increase energy, recovery and mass. At first I was fine but, now I have been experiencing blood in stool with increased pushing to relieve myself. I had this problem once before when using Creatine. I found out force factor has Creatine in it can it be the use of this product? I stop using before and the blood stopped. What ca it be?