@Diamonddusty I'm exactly where you are now. 10 years without sex, he's not bothered, seems to ignore the fact I've told him how unhappy I am, and we rumble on. We too live pretty much separate lives, he does his things, watches his programs on telly (politics politics politics, and completely the opposite side from me), even buys rubbish from the corner shop for his tea while I make a proper meal like a normal person. It's a very long story.
One example from yesterday - he got ds to ring me to see when I'd be in from work (he wfh) so I could 'fix his computer.' So when I got home, he said he'd tripped over the laptop and now his headset wasn't working. I fixed it in 5 seconds - just by switching the headset back on, ffs. And then he went off on a big "oh I'm so stressed" rant, and when I said there was only me and the boss in at work and we'd been busy (i.e. really really stretched) obviously his problems were bigger.... Never mind sticking up for Boris Johnson and Priti Patel later on in the evening......... unattractive to say the least. And he wonders why I want to spend as little time with him as possible.
@adviceseekingnamechanger I got cancer too, and went to all the appointments on my own, and even spent Valentines Day 2016 in a hospital bed, on my own, til he came to pick me up on the night time. Yes he brought me some garage flowers, but I got home to an empty fridge and a full washing basket...
OP, you say My happiness is important... I just don’t know if it’s as important as all of the other things. This is exactly how I feel, and it's utterly paralysing isn't it 
The bottom line is, I want a loving relationship, including sex, but not with him. Not in a million years after everything. I want to be happy. We're allowed to be happy OP. I hope we both find a way xx