Hello Kat Jo,
Type O's tend to be more acidic. They eat more protein. You'll find you'll do better including lots of foods high in minerals. Sea vegetables are the highest. Dark green, leafy vegetables are also very high in minerals.
Begin your day with a glass of water containing the juice from half a fresh lemon or lime. Drink plenty of pure, non-chlorinated, non-fluoridated, high pH (alkaline) water every day.
Take a look at the "General Dietary Recommendations" on my web site at www.TheNaturalHealthPlace.com. Those are all good suggestions for all blood types, but especially type O.
For immediate relief of acidity and stomach upsets try aloe vera juice. A tablespoon at a time is usually enough to settle things. If you need more at first and/or more frequently, use it as needed.
Best of Health,