Thank you so much for posting this, KRA. I came on here today because I am having a very hard time with this same issue, and was hoping to gain some insight, and I thankfully came across your post.
I broke up with my XABF in October after discovering he was planning to cheat on me. I also found out that he was still drinking, although to be honest I think I knew that deep down. We would have been together for 2 years this Tuesday. I went through a phase of horrible sadness, followed by relief and clarity and feeling at peace...but for the last 2 weeks or so I have been having a lot more ups and downs.
Mind you, I have not seen my ex since the day I broke up with him, nor have I talked to him on the phone or through text. We did exchange some facebook messages and e-mails, but his last e-mail to me was a month ago and I told him not to contact me again. I miss him so badly it feels like my heart is rotting. I know I was miserably unfulfilled a lot of our relationship, yet it takes everything in me not to turn around and call him.
I have no idea what you are and are not doing, but going NC is absolutely necessary. I only began to feel better (before this current rut) when we stopped communicating. I do not look him up on Facebook or anything like that either. I imagine he is doing much of the same he was before, and your ex probably is too. On the off-chance that losing me was enough of a wake-up call for my ex, I'm glad I served that purpose...but at 26, I don't see that happening. There is a reason they are our exes.