Addera... no pharmaceuticals?!
There isn't a chess solution to that problem. If you can't focus on a game of chess and think through a position then, as you said, you likely have that problem in other areas of your life and you need to work on your concentration abilities in general.
In playing chess, I come accross only one pitfall: I cannot organize my thoughts efficiently or quickly. This problem arises in several other areas of my life, but I think it's safe to say other players have encountered this issue and have some sort of solution. I have done a general search for chess strategy, but I haven't found anything that speaks about concentration techniques. I can't be the only one experiencing this problem. Any ideas on thinking more clearly (and please don't reccomend any pharmaceuticals, just honest tactics for concentration)?