There are other things that I'm dwelling on that are causing me to feel blah.
I think you're on the right track with this. If you were fine before in R and now you're not, and if he's not the one who has changed, that only leaves you. At this time of life, and after a really big weight loss, yeah.. some midlife angst and even depression are real possibilities. You also said this..
Now that I'm feeling like I'm worthy of taking care of myself...
That statement might be an excellent place to lean in and start working out how you really feel about yourself.
In terms of what helped me put my anger away regarding the adultery, the main things was ownership of my choice. That makes it sound like only one choice, but really, when you think about it, we choose every day what ground we're going to stand on. I'm not a little girl without agency, and yeah, once upon a time my agency was robbed from me. I didn't have all the facts when I made my daily decision. But now I do, and I decide and have decided every day since then. Who should I be mad at about that? I'm the one who chooses to be here. I've had my chance to choose otherwise and I have that same chance every day. It doesn't matter that making another choice would be difficult or that it might not meet my priorities as well. It matters that the buck stops with me on that choice. I am not a prisoner of anyone's machinations but my own.
Sure, it's hard to make other choices when you've got kids and car payments, insurance and mortgages to think about. But what are we saying with that? We're saying that there's value in the domestic arrangement. Again, that's a choice, security over love. Who's to blame for that? The guy who messed things up doesn't have a time machine. He can't fix it. There's no choice which changes the past. We can only act in the present with the facts we have now.
You chose to invest these past eleven years in this relationship. That's on you. And yeah, that sounds kind of harsh, but it's not meant to be. It's actually meant to be liberating, exhilarating, empowering. When you really FEEL your power, the sensation of having been victimized dissipates. Regrets are no longer stagnating, but rather a learning curve upon which future choices can be made.
You're in a really uncomfortable head space right now, but I promise you, the best investment you can make in your future is getting right with who you are today.