The only way to put your mind at ease, (if you're that concerned) is to see the Dr. and to have the colonoscopy.
I'm 51 and just had my first colonoscopy last Monday (Nov 28th). Like you I was terrified to have one so I put it off a year. I have to tell you, that although the prep isn't fun, it's doable. The colonoscopy is nothing. I felt like I took a minute long nap and that was it. I didn't know or feel a thing.
It would be worth putting your mind at ease and a lot less scary IMO, than wondering annd worrying about having colon cancer.
I read a lot on the internet too and have thought I had symptoms for all kinds of illnesses, which turned out to be wrong.
Hope you are able to get some peace about this.