What Causes Blood From Anus?

In the past few days, I've been needing to go poop several times within the same hour or so. The first couple of times, I go, and I'm able to poop, but the few times after that I am unable to get anything out. Today, I woke up, and I still have that same urgency of going to the bathroom, but there's blood coming out of my anus now. What do I have and what should I do?