Once in a month im having a rectal bleeding, it started this august and in december i experince rectal bleeding for i guess 3 days during i poop and im having a diarrhea since december 20s until now and somtimes my stool is a watery dark green stool and im having a stomach pain, especially during i poop, im just only 17 yrs old. Can you please tell me what is this? Thanks you