Cold turkey method symptoms and conditions

I have itching, pain in the abdominal area, sometimes panic attacks, and sometimes drowsiness.
The pain I took it for has gone away now, but I still keep taking it cuz I feel like crap when I get up in the morning, runny eyes and nose, and an anxious feeling, with no energy. I take a perc and drink some coffee and I'm good to go. Think I'm addicted? I do.

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.