The state you describe sounds very familiar to me. What helped me a great deal was to simply stop drinking coffee.
The first few days after stopping my concentration was completely destroyed, I couldn't focus at all. After about 2 days things started clearing up and I got back my calm and focus.
Most of the people I know consume coffee all day long, every day, and don't seem to be affected in the same way I am. Just thought I'll mention it, in case it might help!