Generic versus Label Brand Medication

Has anyone else had negative comments about using generic brand medications versus Brand Named medications.  In my case I have been getting the PPI generic brand Meprazol rather than the prescribed Label Brand Losec 20Mg. The chemist told me there is no differnece but I'm starting to wonder. My symptoms from the diagnosed gastritis from a endoscopy are not going away after 8 weeks. Mainly gassy feelings, slight feeling of bloating, slight constipation then 2-3 BM's in one day.   I don't get any ongoing or sharp pain in the stomach area though.
My father tried the generic brand and his heart burn associated with his hiatis hernia returned and promptly dissappeared when he returned to the actual losec. Makes me wonder if the same thing is happening to me.
Am going to the doctor again this arvo and will be asking him the same. Will let you know how I get on.
Cheers
Dooges