If you feel gas and bloating after eating meat then your problem isn't your blood type, but rather, your digestion. The solution is NOT adopting a vegetarian diet (for which no human is genetically adapted) but it is fixing the poor digestion. In all likelihood you are hydrochloric acid deficient and may also have poor pancreatic exocrine output (which may also relate to the poor HCL production). Low thyroid issues, stress, high carbohydrate/low protein diets and zinc deficiencies (brought on by either low protein diets or diets rich in phytic acid-containing legumes and grains) are all potential contributors to poor protein digestion. Adopting vegetarian or (god forbid) vegan diets only serve to worsen this issue--though may temporarily "feel better". Long term you will develop protein/amino acid insufficiencies that can lead to innumerable mental/emotional and physical problems, as well as extensive mineral deficiencies and endocrine imbalances. I see this all the time in my pracice and it is an extremely difficult set of problems to fix.
I am a "Type A" blood type on what amounts to a "Type O" diet and have superior health. The blood-type diet theory is full of holes and hype and constitutes rather poor Science (nearly all in vitro-based science--NOT in vivo). Whatever partial truths may be contained within it overlook fundamental human physiology and anthropological history.