Do you have any blood in your stool - either with normal bowel movements or the "blowouts"? Any pain? Is your appetite affected? Fever? Unexplained weight loss? Anemia?
Without any of those, it isn't like Crohn's or UC, but if it would make you feel better to get more testing done, then push for it.
I have IBS, and get flares with stress. I also have certain foods that trigger flares. When you get a flare, you should track what you've eaten in the 24 hours prior to the "blowout". You may even have some food sensitivities and not IBS, or you may have both.
Here are some basic guidelines for diets for IBS. Keep in mind your mileage WILL vary. I can eat some foods on these lists, and not others. Also, sometimes I can eat a food and be fine, and others, not so much. Some foods I can eat a little of, and that's it.
You'll notice these lists all have the theme of "5 foods to avoid", "16 foods to avoid", etc. There really is no set list - you'll have to figure out which, if any, foods trigger you. I just wanted to give you a starting point.