How can I stop thinking of everything/one in a sexual light?

I am 21 year old female- virgin. I suppose it is natural being young and everyone around you is doing it- TV and advertisements and internet doesn't help. Whenever something comes into my mind that I do not think it appropriate - I immediately intercept my thoughts with another- change topics in your head. Don't follow the dog in your mind, he may take you down a path you may not want to go to.