Please some advice !?

Here's the situation : I was scheduled to attend a job interview for a job that I didn't really want. Instead of going, I called the employer later on and thanked her but said that I had found another job. Somehow, the employer called my cell phone (which I had left at my in-laws) and was asking where I was. So now, my in-laws (whom I'm always trying to please) think I went to the interview because I lied. By the way, lying is terrible and I realize that but out of desperation to please them I told them that I was a little late for the interview and that's why she called looking for me. I feel absolutely terrible. I have told my boyfriend the truth and I doubt that my in-laws would ever discover the truth , unless they came across the manager of the place which is highly unlikely. So the chances of the truth being uncovered are slim, but I can't help but worry about what would happen and how ashamed I would feel if they did find out. I think I would have to break up with my boyfriend... can someone please give me some advice... I know lying is bad but I need something to make me feel a little better, I'm not sleeping or eating and it's tearing me up. Help !