If not, maybe op can reframe and grab life by the horns.
Health issues can be immensely stressful, and what is required to provide the best logistical and diagnostic support is very different from what is required to be a supportive partner and emotional caregiver. Doctors often fall into the trap of treating the disease and ignoring the patient, but at least that aligns with their job description. It is quite easy to do the same as a partner, and that is NOT the job. For certain personalities, it can often be a massive relief to disappear into searching the web and poring over medical research studies -- the key word there is "disappear". Plus, if someone is suffering physically, you can't really require them to have (what you think is) the "appropriate" amount of gratitude for what you're doing for them. (And physical suffering is always going to lead to mental suffering unless they're a 1000-year old enlightened monk.) You can be quite proud of your savior cred, and your partner can very reasonably tell you to shove that pride up your ass.
It's not about whether you're good enough or not. We all start with woefully naive views of how robust our relationships are. We get together as certain people at a certain time. Living together deepens and widens the basis for the relationship, and we'll all fool ourselves into thinking that nothing can break that apart. But fast forward a decade or two, and upend one or the other of your lives with a health challenge or some major life event, and you'll soon discover that you're in new ground and have to learn a bunch of brand new skills that you never needed before. And there's no particular reason why this person X who you bonded with years ago in environment Y is going to be easier to learn with than some random person off the street now that you're in environment not-Y with a different person X2 who evolved from person X -- just as you've evolved (or devolved) into Me2 from the Me you were. Especially not with the added challenge of a long history together of frictions and irritations that never mattered enough to tip things over the edge but do now in the new environment.
For the record, I'm still married to my X2 in my very-not-Y situation. For now. But I've seen enough that I would never look down on or even be surprised by the dissolution of even the strongest-seeming relationships when a novel challenge comes around.
Back to fairy tales -- Prince Charming's main claim to marriagability was his willingness to make out with a hot living corpse. Are you so sure your own claim is that much superior?
This is overly strong. X2 is likely similar to X and Me2 is similar to Me. X2 is certainly more likely to get along well with Me2 than a random, but far from guaranteed (which proves your point, but I wanted to rein in the pessimism)
My brother last year went to the doctor with an ear ache. The doctor prescribed him some liquids and pills. Only after he left he realised the doctor never even looked into his ear!
Human relationships are brutal sometimes. I still choose to treat others the way I would want to be treated, and some people _actually_ reciprocate, and you eventually learn who is who in your life, but this requires that you be open to the fact the majority won't, and that you will sometimes feel betrayed and used. You just have to accept that it's your decision to make, and decide what kind of person you want to be.
Other commenters are also probably right to one extent or another, the dynamic of the relationship probably changed pretty dramatically and that can create problems regardless.
Anyway, poor old AgentMasterRace probably feels like a depressing episode has turned into something they'd rather it didn't. Sorry for pontificating over your traumatic(?) event with allusions to my own. If I'm reading the meaning of their username correctly though, I feel less bad about it, lol.