Medical/health help (bloody stool)?

So, I've already talked to an online doctor I trust who has helped me a lot in the past, but I wanted to get a bit more of an opinion on this.

Back on June 10th I had an appendectomy. Since then, my bowel movements have varied from normal and mostly to diarrhea, but never any constipation except for a few select times. I still have the occasional, dull/very faint ache in my right side from the surgery but barely.

On November 1st, I went out to eat with my niece, and both of us had stomach problems that night (severe cramping). That same night, when I went home, I started to develop a cough. The next morning it had turned into a full-blown severe cold, with coughing, severely stopped up sinuses, and slight fever. Today, I'm feeling a lot better; My ribs and back are sore from coughing but that's it. However, when I went to the bathroom, my stool was bright red and so was the toilet water, but not a lot of blood on the toilet paper when I wiped. There was only a little when I wiped the first time, but none after when I wiped again.

I haven't been eating a lot but I've been drinking A LOT of drinks with red coloring, like fruit punch and kool-aid, as well as drinking energy drinks, on an empty stomach. I have no abdominal pain, no fatigue, no fever, no other symptoms at all aside from red stool.

I feel completely normal aside from the anxiety I have from this though.

What could this possibly have been caused by? Does it sound serious, and at what point should I go to the doctor?