I have walked the journey, but not the phase that you have with your H coming back. So, unfortunately my take is more theoretical than experiential perspective.
As Sia pointed out, I am wondering at some subconscious level you are doing the 'what if' scenario? Seeing the life your BFF is living, are you comparing your life to hers, and particularly decisions you made. Are you feeling something is missing because of a potential life you might've had if you hadn't taken H back? More questions than answers lol.
I am also wondering if you're somehow struggling with letting go of the past - life with H pre-affair and then BD and the aftermath. I do have experience with that struggle. The issue there is not the recognition that there is explicit baggage that needs to be dropped, but dealing with the fear that once you drop it, it's never coming back on your shoulders and you have to walk the path forward. Even though intellectually you know it's going to fine, part of you is wrapped up in that baggage as being part of your identity and story. Letting go means you have to change your story, which is scary because that story is a source of comfort and retreat. It's tackling that fear and seeing yourself differently where the challenge is. I am just curious to know how you think of yourself? Are you self-victimizing yourself with the story of what happened and that it will always continue to define you? For me, making that marked difference between being victimized in the past, and not a continuous victim helped.
The other thing about what you feel 'missing' in your M, are you waiting for your H to figure out what that void might be and fill it? Even though your R will never be like it was in the past, can you come to a place of acceptance on that? I don't mean resignation to that fact, but accepting that going through what you have gone through cannot possibly salvage the R in an intact way. The other piece on this is - what do you want your M to look like? Don't compare it to the past, but look towards the future. If you're not going to D and walk away, what does happiness and fulfillment in your M look like? And can you take ownership of that and make it happen, with his partnership?
You may feel like your tank is full, which is great, but you still need time for yourself. Tank is full, but not full enough for you to take active steps yet. Maybe you sense that broaching this is going to be another round of exhausting work and you just don't want that right now - which is completely fine.
I am sorry that you're going through this and I don't want to chalk it upto ups and downs in a relationship. I do want to feel the same things you noted when I get into a R. Have the strength for you to do you. I wonder if you feel any pressure to do something because you know he's unhappy and he sees it in your disappointment. Well, that's his bag to solve and overcome his insecurities.
Keep posting and sharing your journey. There's just so much to this and every bit of insight into the full path helps.
