Creatine could cause this problem, as Hemorrhoids can be caused by dehydration.
I'm genetically pre disposed to hemorrhoids, so I have to watch my water intake very closely.
The advice to go see a doctor is very solid, but a couple questions before you go, do you have a constant itchy or burning feeling when this occurs?? Hemorrhoids feel like you didn't properly wipe the last time you went. So if you're not feeling this sensation during other times of the day, you don't have Hemorrhoids, you have a totally different condition.
Second, is the blood actually in your stool?? or is it there when you wipe?? I know, gross topic, but if it's in the stool, that's an internal problem, probably liver related or colon. If it's just there when you wipe, then you're more than likely experiencing hemorrhoid flare ups.