My wife found my hidden ?

Im in therapy because i am addicted to and masturbation. I had told my wife i ha thrown all of the away, but i had hid some under the mattress. Yesterday while he waa gone to the grocery store i went to get it and it was gone, so i know she had to of found it! She hasnt said anything about it but i want to apologize because i lied to her. What should i say? Im trying to save my marriage and i know that ahe feels like im not trying, but i am!