Hi

I don't think anyone can tell you what it is without you having the investigation. From what I am aware of Chrohns and IBD usually present with loose stool and bloody mucous. But, don't let that make you think that it must be cancer then. 

I was unable to empty my bowels and also the feeling of incomplete evacuation causing pain and discomfort. I had bloating and severe abdominal pains starting nearly 8 years ago. For the last 4 years I have been taking medication for it as it turned out to be IBS type C with visceral hypersensitivity. I'm not saying that is what you have, but just that there are other reasons than cancer to suffer with bowel symptoms. Not that what I have is a walk in the park and is life-altering, but it is not life-threatening. 

I did also have blood in the toilet bowl and on the tissue. That was haemerrhoids which I have had a haemerrhoidectomy. 

So, there are less severe reasons for your symptoms sometimes. It is good that you are being checked out to see what is going on. 

It must be especially worrying for you given your Dad's experience. But, there are only certain types of bowel cancer that are hereditary which is rarer. 

I hope your colonoscopy brings you some good news.