I've Had Pain (throb) In My Lower Right Abdomen. It

I've had pain (throb) in my lower right abdomen. It first started with lower back pain and mild diarrhea last week. I had a pelvic ultrasound today. (Which was quite painful) The radiologist said he couldn't find anything alarming. Tonight, after I wiped, there was a discharge with blood in it. What do I do now? What's happening?