Omeprazole and omeprazole 20mg

I've been taking Prilosec OTC for 3 years, 20mg a day. All problems with my acid reflux disappeared. HOWEVER, I switched to generic Omeprazole 20mg and the heartburn reappeared. This has been awful! I thought they were supposed to be the same drug! I switched back to Prilosec OTC and my stomach is finally feeling some relief.

I have been taking OMEprazole for approximately 2.5 months and recently I feel dizzy to the point I want to get a doctor appointment to have an MRI or CT scan on my head - my fear is that I have a brain tumor. I feel dizzy as if I am going to pass out, occassional sharp pains in my head and I feel sick to my stomach. I also feel extremely tired and recently like the left side of my body is weak.

I am going to stop taking Omeprazole today to see if this is the side effect of the medicine. Anyone have similar experiences. If so, how soon do they stop after you stop taking the medicine? I was concinced I had a brain tumor - not so sure now.

PS I am a very healthy 50 year old who is a marathon runner. Lately I have sucked on my runs due to exhaustion.

I have been taking omeprazole 20mg daily once for the last 9 months. After one week of taking this medication I started developing mild symptoms of dizziness, fatigue, sweating of hands, weekness of legs, panic and nervous attacks especially while driving. Slowly the symptoms became intense and now I cannot drive at all. Initially I was not aware that these are the side effects of omeprazole. I did EKG, MRI of brain, Cardiac thorough check up and tests, all normal.
Finally I traced back the time of the symptoms and the start date of this medication, it exactly coincided. Can anyone tell me if these symptoms are reversible. I have stopped taking Omeprazole.

I HAVE BEEN TAKING OMEPRAZOLE 20MG FOR FOUR MONTHS AND HAVE BEEN SUFFERING FROM MOUTH ULCERS SOMETIMES UP TO THREE A WEEK AND A TREMENDOUS AMOUNT OF GAS