ITA that we don't know what Deacon was like before he got sober. I can imagine though, because he's such a baby now! He must have horrible.
I do recall Rayna and Deacon talking about how he regretted she left him when he went into rehab and she asked how as she supposed to know that that was the time it was going to stick. So, that leads me to believe that the last time he went was when she walked away from him and married Teddy. So, that would mean that he didn't have much drunk time after Rayna got pregnant. It was too late to go back to Deacon though, because she was married to Teddy by then.