Pach, yes, as you've discovered, alcohol can last awhile. The day before I started an outpatient addiction treatment program I had 2 glasses of wine (my idea of tapering, lol). The next morning, they did a drug test and my BAC was 0.01. Though that's not high, I was floored that it even showed up from 2 glasses the afternoon before!
You sound like you have a lot of strength and I believe you can and will do this! You will find lots of good support here.