I have had a similar experience, It really scared me, I had it checked and it turned out to be a hemorrhoid that was irritated from being a little constipated from the diet. Bright red blood is usually from something like this and dark blood shoild always be checked. I think you should be checked anyway just in case it's really irritated, and maybe something else. The other thing I thought of was are you close to getting your period by chance, or on birth control pills and could possibly have some breakthrough bleeding? Just a thought... But go to the doc and put your mind at rest!