Obsessive Compulsive Disorder. Obsessions are recurring, intrusive thoughts that disrupt your day to the point that these thoughts are your only focus. (Ex.: Did I unplug the iron?) A compulsion is an act you must do to alleviate or lessen the obsession (Ex: You go back to check the iron over and over again).
For more information, please read my article about Obsessive Compulsive Disorder