There is no pill in the world that will help you come clean to your wife,whatever you have to tell her please do it and then hopefully she can understand the reasons why and then you may feel better and together can work on making your marriage work.
Welcome to the forum. I'm not sure what it is you have to tell your wife, but obviously keeping this secret is tearing you up. There is no pill or anything really that can "make" you come clean with her, but perhaps seeking some counseling would help. You could confide in an uninvolved 3rd party person and discuss everything that would be involved in finally telling your wife this secret. A therapist could help you go thru the motions, discuss the possible resulting scenarios and help you work through how you'd deal with it. A therapist could also help you explore this secret...what brought you to do/say/think whatever it is that is making you feel guilty and what maybe brought you to that point...to help give YOU some peace you need. You could also have the therapist help you decide if "coming clean" is even the right thing to do. I'm not advocating secret keeping, but every situation is different. Jumping the gun and telling her to relieve your own guilt isn't necessarily the answer.
Not knowing what plagues you...I will generally say this...we're all human and despite being good people, we don't always make the right decisions in life, and as a result, end up hurting ourselves and the ones we love most in this world. Bottom line, you need to address this as it is causing you a lot of anxiety. Instead of just blurting out your secret to relieve yourself of the guilt...I would strongly recommend that you explore all of this with a professional first. It may make a difference in the way this situation plays out.
Good luck...if you want to discuss it more, we're here, and we don't judge people. You're safe here.
I don't think you can find the answer in a "pill."
I have been married 28 years and I can tell you even if I was having an affiar, was suffering from drug or alcohol addiction, or anything I could think of - there is nothing that would help my relationship more than sharing it with my wife. After 51 years of undiagnosed thyroid diseases, temper rages, severe skin disorders, a problem with being too hot all the time, occasion depression, routine severe ansxiety, and on and on. Where would I be now without her?
Dead probably.
Whatever she needs to know about, that you can't tell her, can be shared in therapy or with a very close family member, or religious counselor if you feel you need a "buffer." But I doubt you give her much credit if you don't go to her directly. As your wife, she deserves that, and you promised it when you took your vows.
If you have a medical condition, are depressed or suicidal. You need to speak with both her and a doctor, together. As soon as you can. It may mean your life.
Anything you can't bear anymore, needs assistance. She's the first person in you life, and the first to help. Give her a chance.
Best in Health.