If you've been hanging around on this board reading various threads, you probably know that it takes a great deal of patience to find the right medications for your individual body. In the U.S. it is more common to use meds in combination and this process takes even longer as the pdoc usually wants to introduce them one by one.
For example, my 25-year old son takes 3 mood stabilizers: lithium, Lamictal and tegretol. This is the combination that works for him with the fewest side effects. I can remember a time before he was properly medicated, that he could not read or even watch a movie or long TV program. He had difficulty sitting still that long and couldn't concentrate long enough to read. Your body will adjust to some extent. If not, there are other meds you can take to help your mind refocus.
Things will get better. Unfortunately nothing happens fast. Try to be patient. Talk to your pdoc about it, too. He may have some suggestions.

Tsohl