Hi,
Thank you for posting your query.
I have noted your symptoms. 
There could be various possibilities that could explain your difficulty in concentration. These could include 
electrolyte imbalance such as low sodium, low sugar, etc. Also, lack of blood flow to brain (
ischemia) could be the underlying cause. We should also rule out 
stress or 
anxiety.
A detailed neurological examination would be helpful.
I hope my reply has helped you.
I would be pleased to answer, if you have any follow up queries or if you require any further information.     
Best wishes,
Dr Sudhir Kumar MD (Internal Medicine), DM (Neurology)
Senior Consultant Neurologist
Apollo Hospitals, Hyderabad,
For DIRECT QUERY to me:  http://bit.ly/Dr-Sudhir-kumar 
My blog: http://bestneurodoctor.blogspot.com/