Why can't I see the video I recently watched?

I watched a secret video my girlfriend was hiding and I cant get it out of mind. Should I tell her, morally?

• OK, long story short, I took a 4 month break from the girl I am currently in a 3 year relationship with while I was traveling, and in that time she did see someone else for about 2 months - I did not see anyone else on the other hand. I am not mad about it, other than at my self, as the break was my idea; in general I am fine with it and happy to be with her. BUT I use her computer a lot (with permission of course! I am saving to get a new one myself), and several days ago I was looking for a picture she had taken I wanted to upload and was kind of looking through really random folders and I found a sex video. It is such a coincidence I ever looked there, but I kind of instantly knew what it was. I watched a bit when I found it to see what it was, but stopped when the clothes started coming off. So I debated whether to watch it for several days, and finally I watched a bit more, and stopped watching again when the foreplay intensified. Watching made me sick but I just couldn't get it out of my head, so I finally watched the whole thing. The whole video is about 40 minutes, but it felt like eternity to watch. In the video she seems a bit drunk, but she even moved the camera herself, so obviously she knew it was filmed. Now that I gave in to my curiosity I and watched it, I feel so guilty that I invaded her privacy and saw what I shouldnt have, and I cant stop thinking about what I saw, especially certain moments. At first I was angry she had kept it, but now I feel worse about secretly watching...so should I tell her or what? How do I explain that I watched the entire thing??

• Answer:

  the proverbial pandora's box