In ghusl it is sufficient to make the water reach all areas of the body

I have sent this question before but I still am confused as I did not get a detailed answer. I know very well that my questions may seem silly to you and do not deserve to be answered. I am suffering from whispers, and so many other people are suffering from Obsessive-compulsive disorder (OCD). Please do not do not tell me to browse similar questions, as I will not convinced but by your answer to my specific problem. For example, making ghusl after the impurity of an intercourse, I want to know if it is adequate to stand under the shower and pass water allover my body? Do I have to wash between thighs or only on what appears of my skin? As for wudu’ (ablution) I wash my organs once only so that it does not take long time.

Praise be to Allaah.

Firstly: 

We ask Allaah to grant you healing and well being always in your religious and worldly affairs. 

What must be done when doing ghusl following janaabah is to make the water reach all areas of the body, including the area between the thighs. If you stand beneath the shower and the water reaches all parts of your body, and you rinse your mouth and nose, then you have done ghusl. 

Secondly: 

It is permissible to do wudoo’ washing each part of the body only once, but it is more perfect to wash each part three times, as is well known. 

If you only wash each part once until you overcome this waswaas, there is nothing wrong with that in sha Allaah, and you should seek the help of Allaah by praying to Him (du’aa’) and asking for healing. 

We ask Allaah to protect you and make you well. And Allaah knows best.