I am also Type O and have been vegetarian for 62 years. I have never heard of anyone with IBS benefiting from eating meat - quite the opposite. Do you eat dairy? If so, you may want to quit, it is the worst thing for the digestive system, also soy may have a negative effect. Your best bet is to eat as much of your food as possible unprocessed - raw is good. Keep it simple, read labels, avoid chemicals like preservatives and never consume high fructose corn syrup. Eggs are probably okay, but be careful with fish - the older and larger the fish the more likely it is that it has consumed a lot of mercury and other pollutants - tuna is one of the worst. Make sure you get enough fiber - flax seed meal and or Konsyl work well. For a general supplement I recommend Vitamineral Green by Healthforce Nutritionals.

Good luck, stay well and stay vegetarian.