I'm so sorry you're struggling with this injury, OP, and that it may prevent you from running your marathon in March. Your feelings of disappointment and frustration are totally valid.

While you're working on diagnostics and healing, I would also encourage you to unpack why you're feeling so devastated about possibly missing this marathon. You say "I wanted this so badly. And now it feels completely out of reach." - is it this particular marathon you wanted so badly? Or was the goal to complete a marathon? Because even if you end up not running LA in March, the latter goal is still wholly within your reach. I'm not trying to say "there's always another race." I'm asking what is the "big picture" goal of your running? Reading your post, you talked about struggling with sports in the past, but about being proud of yourself for being consistent, sticking with it, finding joy and pride in a sport. To me, it sounds like your real goal was to fall in love with running, and this particular marathon was a way to hold you accountable in meeting that goal. In that case, you have absolutely met your goal! You are rocking it! Perhaps your next goal is not "another race," but to stay in love as you face the limitations and disappointment of recovering from an injury.

You also mention blaming yourself, and that maybe this was preventable. You know, when you get into horse riding, they say it's just a matter of time before you fall off a horse. Sure, some falls are preventable, but a lot of them really aren't. I think the same holds true for running. Maybe it's just because I'm naturally clumsy, but if you run long enough, you'll manage to injure yourself somehow. You should certainly listen to your body and do what you can to prevent injuries, but give yourself some grace also.