Stomch Gone Haywire...any Insight Please???

I am 18 years old. I developed an eating disorder when I was 16; a mix of both bulemia and anorexia...However now for the most part it has been under control for the past 5 months. I am a freshman in college, and this past semester I was struggling with my math grade so during finals the stress was momentous. I had two nosebleeds which I never have gotten before, and at the same time my stomach started to go crazy. I would feel extreme bloat even if I wuold eat the smallest bit of food, I wouldnt feel hunger for long periods of time due to this bloat, at times I was extremely gassy, and constipation was prevelant for days at a time. This all started about 2 and a half weeks ago. I went to the doc who told me to take fibercon pills...So I would take about 4 throughout the day. It helped, but sometimes the bloat and discomfort would come back. The doc said it may be ibs. About 2 nights ago I was awakened at 4:30 am from a feeling as if my intestines were being twised inside of me, and I had to run to the bathroom 5 times in 40 minutes. The first 2 bowel movements were rather solid, the 3rd was a bit more loose, and the last 2 looked like the salad I ate for dinner the night before. Since then, my bowel movements have been very black and a bit tarry, and even if I sit down to pee a bit of stool comes out without me even trying. Sometimes mucus is present..However abdominal pain is extremely minimal. My grandfather died of colon cancer, my mother has ibs, and brother has been recently diagnosed with sligh chrone's at the age of 22. Obviously this is something to be worried about...But when my mother indicated that tarry stool is a syptom of colon cancer I got really scared. For the note, my eating habbits are extremely picky..I eat very very little fat, and have a higher concentration of protein than carbs, and I am an avid gym-goer. Does anyone have any idea what the hell can be going on???? Does this sound alot more extreme than ibs???