Welcome back strange angel. You might just view this a "slip" but in reality it's a pretty clear sign of a much larger problem. And apparently you haven't fully accepted the problem if you thought it would be ok to "have a few".
Unfortunately there is nothing you can say that will undo your actions last night. By picking up that first drink you basically accepted responsibility for everything that happened afterwards, even if you don't remenber it. And it's not your fiancées fault for saying it was OK to drink....you made the choice.
What you CAN do however is accept your alcohlism and committ 100 percent to not drinking right now. And develop a plan to follow every day than will help you stay sober. We can help you with that, and over time your actions by staying sober will speak volumes.