What Causes Difficulty In Focusing And Comprehending?

I have a very difficult time staying focused. I am also very impulsive and procrastinate is my middle name. However I do not see myself as hyperactive. I recently enrolled in school and had to almost immediately withdraw because I could not focus. I have to read questions over and over and sometimes still do not really understand. I remember dealing with this in school but was always too shy to ask for help. As I age, I just notice that it is becoming more and more of a problem. Could I be dealing with some form of ADHD?