It could be Diverticulitis, or it may be something else. I would immediately go on a clear liquid diet and either call my Dr, for an immediate app. or go to the ER.
Diverticulitis that goes untreated (antibiotics) and gets worse may cause a perforation, or another life threatening complication. Please see medical professionals. NOW

Is it possible to have attacks of diverticulitis that come and go? I had two attacks Saturday and Sunday and pain in my left side all day yesterday. Today I have slight pain in my left side.

I am assuming they are all 1 attack that isn't healing-----It may take up tp a month for an attack to heal. If it keeps coming back, it usually means you need to be on a liquid diet for a few days, then when you SLOWLY start back with LOW fiber to go slow and eat only small portions of food at a time

I would second gem's advice. That's what it sounds like to me. Except that if you don't carefully let it heal with a liquid and then a soft diet, it can take even more than a month to heal. It can become chronic.

I went to the ER yesterday and they did normal x-rays, blood tests and urine specimen. They wanted a stool sample but I couldn't provide one. They said the x-ray showed lots of stool and lots of air. Blood tests and urine specimen were normal so no infection. I was referred to a gastroenterologist for further testing. All the doctor said was that passing hard stool over long periods of time could have irritated the lining of my bowel causing the maroon colored blood in my stool as well as the pain with bowel movements. He said nothing about the pain when I eat. He said to eat more fiber and now I have to wait for the gastroenterologist to phone me. Today, I'm still in a lot of pain in my lower left abdominal area and the pain goes around my back as well. I feel weak and nauseous. The gastroenterologist better order more testing. I'm not sure what else I can do.

PLEASE do NOT EAT FIBER

I am so very sorry, But what the Gastro Dr. says is wrong, wrong, wrong. If you want the pain to go away go to a CLEAR LIQUID DIET until the pain is gone, then go to a regular liquid diet for a couple of days. SLOWLY introduce LOW fiber foods for even up to a few weeks.
I understand you need something for the stools, but as long as your gut is causing you pain, DO NOT EAT FIBER.
A lot of Dr's prescribe Miralax as a stool softener. I would try that and see how that works.
If it gets worse and you need to go back to the Dr. I would suggest you go back to the ER rather than the idiot that told you to eat fiber.
If you are still having pain a few days after starting the clear liquid diet go back to the ER.
Did anybody give you antibiotics????

Hopefully you have heard of the famous MAYO CLINIC in the USA.

This is the Mayo Clinics Diet for when you are having an attack. Please listen to them;

A diverticulitis diet gives your digestive tract a chance to rest while your doctor treats your diverticulitis.
By limiting yourself to clear liquids and slowly adding low-fiber foods to your diet, your digestive tract has time to heal.
Diverticulitis diet during an attack
During an attack of diverticulitis, your doctor may recommend diverticulitis treatments.

Your doctor may also recommend that you stick to a clear liquid diet for two or three days, or until the pain goes away.

Foods and beverages allowed on a clear liquid diet include: Broth, Clear soda, Fruit juices without pulp, Ice chips, Ice pops without bits of fruit or fruit pulp, Plain gelatin, Plain water, Tea or coffee without cream.
Diverticulitis diet once signs and symptoms begin to resolve
As you start feeling better, your doctor will recommend that you SLOWLY introduce low-fiber foods.
Low-fiber foods include: Canned fruits, Desserts without seeds or nuts, Eggs, Enriched white bread, Fruit juice with little or no pulp, Low-fiber cereals, Milk, Yogurt or cheese without seeds or nuts, Smooth peanut butter, Tender meat, poultry and fish,White rice or plain pasta, noodles or macaroni, Well-cooked vegetables without seeds or skins.

You may need this low fiber diet for 2-4 weeks or more before VERY slowly starting back on the fiber foods.

To much food can also cause a good amount of pain. Eat small meals for awhile, about the size of half of a sandwich..
I wish you the very best of luck.

It wasn't a gastorenterologist who said to eat fiber it was the ER doctor. Thank you for all of the wonderful advice! I wasn't given an antibiotic because the doctor said that my white blood cell count was normal so no infection. He just did a regular abdominal x-ray without contrast. Would diverticulitis show up on a plain x-ray? He said it just showed lots of stool and air.

I Googled your question about x-rays. The answer I got was that x-rays may show Diverticulitis.

I have had a couple of Dr's almost kill me, during a flare, telling me to eat fiber during an attack. The more people I talk to it seems that a lot of Dr.'s just have no clue about Diverticulitis.

I learned all the important stuff off the internet, and from the most amazing people from a Diverticulitis forum. Unfortunately, we all quit the forum at the same time when a troll drove us off. It was so sad.

At least a gastroenterologist will be able ti find out some answers. I may have a long wait for an appointment. Could the air and stool have masked diverticulitis?

I don't know, Darkness. Try Googling any questions you have.
They will be more knowledgeable than the ones I can give you.
The only other thing I would like to add is please do not hesitate to go to ER if you feel you are worse.
Diverticulitis can be dangerous if there is a complication arises like a perforation occurs.
Please be careful and do not hesitate to go to an ER!!!

I'm starting the clear liquid diet today and am going to the grocery store to pick up what I need. I had pain in the morning that went away in the afternoon and I mistakenly assumed that the flare had passed because I had no more symptoms for the rest of the day until today. My symptoms are back with a vengeance! I should have started the clear liquid diet sooner. I'm going to try it for two or three days then slowly reintroduce low fiber foods as the mayo diet diverticulitis diet suggested.

I won't be hearing from the gastroenterologist until at least October 14th! I called their office and they are closed until then! Canadian Thanksgiving is on October 13th and they are closing earlier apparently. No other doctor works in that office and all other doctors would be the same! It's always like that here.

It could take a long time, I have seen it take up to a month for a flare to heal. Please go slow on changing from the liquid diet to low fiber foods that are on the Mayo Clinic's list. Add 1 LOW fiber food a day and the first sign of a twinge go back to the liquid diet and remain on it for a few more days.
Good luck