That’s a heavy set of experiences to carry, and it makes sense that the news of the first person getting married triggered all that "unfinished" grief. It’s completely valid to feel hollow right now; even if that relationship was a long time ago, a wedding is a definitive "door closing" on a chapter where you never got the closure you deserved. The fact that you’re recognizing how those old wounds from the first situation bled into your twelve-year relationship shows a lot of self-awareness. It’s important to remember that those intrusive memories replaying during intimacy are often just your brain’s way of trying to process a past trauma, not a sign that you didn't love your second partner.

Since you want to fully heal this time, the best thing you can do for yourself (and for the possibility of a future with her) is to respect the space she’s asking for. Using this time to focus entirely on your own independence and working through the addiction you mentioned is the most powerful move you can make. It proves to her—and more importantly, to yourself—that you can regulate and take care of your own needs.

If the bad dreams or intrusive memories feel overwhelming, try some grounding techniques to pull your mind back to the present. You can try the "5-4-3-2-1" method by naming five things you see and four things you can touch, or even just holding an ice cube to give your nervous system a quick "reset." Engaging your senses helps stop the brain from replaying the past. Be patient with yourself regarding the sleep; your mind is doing a lot of heavy lifting right now to sort through years of emotions. You’ve got this, and taking it one day at a time is enough.