Is it IBS or diverticulitis?

IBS symptoms:

Symptoms
The signs and symptoms of irritable bowel syndrome can vary widely from person to person and often resemble those of other diseases. Among the most common are:

Abdominal pain or cramping
A bloated feeling
Gas
Diarrhea or constipation — sometimes alternating bouts of constipation and diarrhea
Mucus in the stool
For most people, IBS is a chronic condition, although there will likely be times when the signs and symptoms are worse and times when they improve or even disappear completely.

More info: https://www.drugs.com/condition/irritable-bowel-syndrome.html

Diverticulitis
The signs and symptoms of diverticulitis include:

Pain, which may be constant and persist for several days. Pain is usually felt in the lower left side of the abdomen, but may occur on the right, especially in people of Asian descent.
Nausea and vomiting.
Fever.
Abdominal tenderness.
Constipation or, less commonly, diarrhea.

https://www.drugs.com/cg/diverticulitis.html

You must see a Dr. as soon as the weekend is over, I , my personal opinion is that you have IBS... but I am not a Dr.