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What sort of tests have you had for your doc to conclude IBS? The only reason I ask is because vomiting is not common with IBS. Have you had your gallbladder and appendix checked?
My suggestions would be to eat a low fat diet high in fiber. Also stay away from caffeine, alcohol, and carbonatation. I suggest also taking a probiotic or eating yogurt. Tea is also great for the gut. Here is a list of teas I mentioned in another post:
Chamomile (soothes the nerves)
Fennel (calms muscles, improves digestion, helps flatulance)
Mint (eases GI trouble, relaxant)
Lemon Grass (antispasmodic, anti-irritant)
Ginger (eases cramping & nausea)
Green (promotes digestion, overall health)