What could be the cause of this case of black stool?

Hello, I've recently been experiencing very dark and thin stool. It is almost black in color, contains what appears to be unprocessed particles, appears very loose and amorphous, and possesses a wispy and almost hair-like quality. I am a young female who has not been taking supplements of any sort or consuming similarly colored foods. I certainly do not eat much and experience frequent stomach upset and diarrhea upon eating. I have purged within the last week which resulted in diarrhea immediately after. Also, in prior months I had experienced persistent feelings of needing to clear the throat followed by the taste of blood in the past. I have obsessive compulsive praying at a rate of about 10 to 20 short times per minute which I feel the need to punctuate with a clicking noise made at the back of the throat, and I believe this could be a contribution to the former issue. Any ideas on the cause of my stool, especially if it is in fact internal bleeding?