Whoishe,
You walked out when you saw it for what it was. That's the opposite of codependency. And feeling pain over the situation is not codependency either.
What would be codependency would be if you were to spend more time supporting him, trying to change / fix him.
The question to work with though is, why didn't you see him for who he was earlier? What was it that fogged your vision? I ask this because I have spent a lot of time asking myself about what it was in my partner that I didn't see for so long that led to addiction and jail for him, and several years of misery for me. It is in pondering this question that I have experienced a ton of personal growth. I won't be snookered again.....
Good work on getting out so decisively. You did better than I did.