Well the bad itching is a clear sign of hemorrhoids. Bleeding hemorrhoids are very common, and aren't anything to worry about. It's the veins in the anus that pop out and can be easily ruptured when having a bowel movement or using toilet paper. They can also be ruptured by anal sex or masturbation.
I get these too from time to time. I find they don't flare up if you don't "push" too hard when doing #2, if you know what I mean. If you do anal masturbation or sex, use LOTS of lube to help prevent hemorrhoid flare ups and bleeding. You basically can't use to much - the more lube you use, the better.
Hemorrhoid ointment such as Preparation-H works well too to keep the itching down and help reduce the swelling.
It's good that you are concerned and noticed the blood though, and thought to ask for help. Sometimes blood in the stool can be a sign of big problems such as colon cancer. Sometimes people ignore it until its too late.
But in your case you have nothing to worry about.