I am going to save an old sex video I made with an ex and lie about it to my bf.
Why did you make that kind of video in the first place.
I did it on a whim, I wanted to see if I could get away with it.
That is a terrible secret to keep. It's not good to keep secrets from your significant other. You should come clean now that you have it so that your bf doesn't find it later on.
I wont tell anyone and he won't find out about it.
It is a big risk to keep secrets from your partner. That can be harmful to your relationship in the long run.