hi, shnookey,
it may not be that something is wrong with you; all it may be is that you need to teach yourself how to concentrate better. have you considered meditation? it's a form of mind control where one learns to filter out distracting thoughts. in other words, in your case it may help slow down the ideas entering your mind or to select just those that pertain to what you're trying to focus on. it will help you to control your thoughts rather than be at their mercy.