What Causes Blood In Bowel Movements?

I had my vagina painted with gentian violet on Monday for a yeast infection. I had sex last night, and I felt a little bit of pain after the first thrust, but no uncomfortableness after that. I then started bleeding about ten minutes afterwards, but it was really light. However, when I had a bowel movement last night and this morning, there was a fair amount of blood in the toilet. I am really scared even though I'm not in any pain nor do I bleed unless I have a bowel movement. I don't want to go to the ER, and it's the weekend, so I can't go to the ob-gyn for an examination. Can I determine whether it's a tear or merely irritation without an examination from a doctor? Please help.