Hi and sorry that you are having pain and distress. Am not a doc, but am well read in various ailments as thru the years have had alot of health issues. Would like to put your mind at ease as this does not appear to be cancer related at all. Your symptoms appear to be viral or bacterial related. That could have created gastritis, which set into motion many other issues. The blood in stool usually could be worrisome if it were tarry or blackish in nature. The stomach grumbling is a benign condition, and has no significant worry. Gastritis is inflammation in the lining of the stomach, and could be whats complicating your situation. I would avoid alcohol, smoking, spicy foods, and try eating bland for a few days. With that an over the counter acid reducer such as pepto bismal or liquid medicine that coats the stomach. Have had cancer twice, and very much doubt that you need to worry that it's part of this scenario. Try this for a few days and see how it goes. Sometimes if it is bacterial additional meds are needed. Viral infections clear on there own given time. Should this continue, a doctor would be your best course of action.
Be well, and hope this helps........Kim
Oh and my stomach rumbles SO loudly, all the time. It keeps my partner awake. Its been making noises since I came back to the UK, we were away in Asia for 4 months overall.