Lots of blood.

Just recently (today), when I've was going my usual (as in for IBS usual) diarrhea/poop and I discovered there's been a large amount of blood that's been coming out with my stool. This has happened twice.
I'm not pmsing, I'm not feeling any pain, I haven't been doing/eating anything weird lately, it's just been...disturbing to suddenly find lots of blood in the toilet.
I do know that I have about 3 visible fissures. But they bleed nowhere to the amount I'm seeing. I would assume that if I had a fissure deeper in my intestines, I would probably feel stomach pain of some sort, which I'm not, and there wouldn't be so much blood.
Anyone got a clue as to what might be going on? I'm totally lost and don't know whether this is serious or not.

ITA. This is not an emergency room situation, but it is something you should talk to a DR about ASAP. If you don't already have a GI, you should start with your primary care physician. S/He can start some testing while you get set up with a GI.