This is from a month ago, so I hope you're feeling better now.
I've been going through a similar experience, on and off over the last couple of weeks, and I really resonate with this bit;
I don’t even really mind all this physical pain and discomfort. The thing that bothers me the most is that I’m completely useless. Unable to think properly apart from a few moments during the day
It sounds like you got much sicker than I have. But it's still having a crippling effect on my executive functioning . I've accomplished almost nothing for a couple of weeks, and I'm meant to be preparing for a live concert this weekend, and then a 2-3 month trip away in a couple of weeks : /
This sounds like a tough situation. From what you've described, the way this person is treating you lacks any trace of care or respect. You deserve better. From anyone you interact with, but especially from anyone that wants to be intimate with you (in any sense of the word). I'm concerned that you're still talking to them, let alone wavering on whether to break up with them.
At the risk of being a bit harsh, I wonder if this song applies? I share this only because sometimes it's easier to see from the outside how abusive a relationship has become. I've you're feeling delicate, maybe wait until you're feeling a bit more robust before you listen.
People with a narcissistic streak are attracted to anyone with weakened personal boundaries. This is often the case with those of us who grow up with undiagnosed ADHD, and other forms of neurodivergence. Because we spend our formative years with a neurotypical-dominated world constantly gaslighting us. We're taught to distrust our perceptions; of what's normal for us, what works for us, and so on.
Two things; self love, personal boundaries.
It's an ongoing journey. Life traumas often tip me back into self-loathing and letting other people push me around. But I keep working on accepting myself, warts and all, and reminding myself that I don't need to be perfect to deserve love, let alone basic care and respect. I keep working on saying "no" when that's the right answer for me, even if other people get upset that I don't say "yes".
There's a book by Dr. Allan Mallinger called 'Too Perfect: When Being in Control Gets Out of Control'. I try to remember to reread this book every few years. I found this really helpful, both for understanding my own obsessive people-pleasing. As well as being more compassionate towards others when they're stuck in obsessive behaviour, without sacrificing my own wellbeing trying to "fix" things for them. Which might help in dealing with this person you're struggling to break up with.
Another book I've found really helpful for my journey towards self-acceptance is The Power of Now by Eckhart Tolle. Tolle's prose is gentle but never pandering. Often confusing, but always in ways that open space for deeper reflection. Each time I read it, I always follow the suggestion to put the book down and come back to it later, whenever one of the little pause symbols appears. Taking some time to absorb each section and observe my mind's reactions to it, and whether that conflicts with or resonates with my more intuitive responses.