Hi Newone,
I’m not sure I have any direct advice, as it’s my partner rather than me who is going through addiction. But there is help out there – your GP (if you have one) can direct you to support/treatment. Or there’s Frank (https://www.talktofrank.com/get-help/find-support-near-you) where you can find local help.
First instance, though, your wife deserves to know the truth. She may already suspect it, but she deserves to be told. And to not be alone in that – it’s a horrible feeling, from experience. Being honest and transparent is hard, but the other option is to slowly wear away her trust and your relationship, and it sounds like you don’t want that.