Welcome aboard Will. This place will indeed help you quit, but as you know, the key word is "help". You'll need to own it...you'll need to put in some heavy lifting. I too was a ninja dipper. It is amazing how F*^(*ed up our lives become trying to both get our fix, and hide the clues. Trust me, you are working very hard to support your addiction. Put that effort into quitting.
I strongly suggest you come clean with the GF and family. Tell them what you're doing, and that you may be an asshole the next couple of weeks. It prepares them for your fog and your nic-rage for one. Number two, they probably already know it, or strongly suspect it anyway. But they have no idea the power you allow this thing to exert over you. Your wife-to-be will
definitely know it, even if she doesn't acknowledge it. Leveling with them will stop the "Let's pretend Will doesn't dip!" game, and possibly give you one more layer of accountability.
Feel free to PM me if you need anything or have questions. Good call coming here...now jump in with both feet.
PS - have you significant other read
the Spouse support info.