So the cause for OCD is unknown and doctors cant find out why people have OCD. 
That is a huge issue that needs to be resolved, I have a couple of friends that have OCD.
Obsessive–compulsive personality disorder
Obsessive–compulsive personality disorder (OCPD) is a personality disorder characterized by a general pattern of excessive concern with orderliness, perfectionism, attention to details, mental and interpersonal control, and a need for control over one's environment, which interferes with personal flexibility, openness to experience, and efficiency, as well as interfering with relationships. Workaholism and miserliness are also seen often in those with this personality disorder. Persons affected with this disorder may find it hard to relax, always feeling that time
loop whereby obsessive thoughts are trapped. Although structural and functional neuroimaging studies have provided a strong basis for this supposition, it is still unclear why patients with OCD develop specific obsessions instead of a generalized obsessive behavior towards everything. While researchers have suggested that a response bias exists toward particular stimuli, such as contamination, the underlying cause is still unclear.
Neurochemistry.
While there seems to be a ubiquitous understanding that neurochemical functioning is responsible for mediating the symptoms of OCD, recent psychopharmacologic studies have found that the serotonin (5-HT