RLQ pain after running

I am a person who has been running for 10 years and who participates in triathlons. Approx a year ago, I noticed that while jogging, I would start to feel some pain in my belly button that would immediately radiate to my lower right quadrant. These are not side stiches, and I normally have to stop running while the pain is there since it is very painful. It usually takes 30 minutes or so of running for the pain to start. I don't have it every time I run, but they seem to be occurring more often. Usually, the lower right quadrant is sore for at least a day or so after the pain starts. It seems to me that the running is moving something around in my abdomen. Also, the other day, I noticed that my stool appeared to have a hint of red tint in it. It wasn't a bright red, and seemed to be mixed in instead of on the surface.

Has anyone had this happen while exercising?

Thanks!