What Causes Sharp Pain Under The Breast After Having Food?

i have had for three days a sharp pain under my left breast. i have noticed that the pain gets sharper after meals and i have like gas bubbles which move in the ribcage and they are very painful. the GP has prescribed me omeprazole 2 a day for the first 3 days and then one a day together with antibiotics. Any idea what this could be? it is driving me crazy and i do not think the doctor understood what the problem is. Many thanks