Or is this absolutely batshit (sex life related)

Yes, all of this.

My first thought when I read your post was immediately 'This isn't really about sex'. And it isn't. It's about control. Walk away.

Honestly I was thinking along these lines. Or that he must have a head injury or a brain tumour. Surely no normal man just suddenly starts behaving like this? He needs to see a doctor.

Jesus Christ - just get rid OP, you've got years and years of this ahead otherwise.

Definitely manosphere shit imo. Check his browsing history if you dare. I suppose then you have to decide whether you want to challenge the misogynistic nonsense he's clearly been imbibing, or whether just to cut your losses. Only you know if the person he used to be is worth the grief.

So you aren’t married and you don’t have a child together. Run far away.

Christ Almighty if he lived with me there would be exploded testicles scattered all over the walls like giblets!!!!

I can't believe any man still uses that thing about the "painful balls" to get inside a woman. Boys used to say this to me when I was a teenager.

He seems to have reverted to the emotional neediness of a very young adolescent, for reasons that I think @JacquesHarlow has nailed very firmly on the head.

Unfortunately this has turned him into such a sex pest that I would want him gone ASAP rather than investing time and effort into seeing whether he could be persuaded by intensive therapy, heavy drugs, or whatever into becoming a normal human being again.

And even if he could be miraculously "fixed":
He is one of those people that is one things after another, as soon as we sort one issue out he will be thinking about the next one.

I hope you don't imagine a bright future with this one, OP, things are not likely to improve over the years I'm afraid. 💐

God, he sounds like an absolute bellend. How do you stand him?

So what are you going to do OP? It's definitely not normal on his part and you've lost patience. Time for an ultimatum?

Has he had a stroke (not a euphamism)? He sounds mentally ill.

Any other controlling, or upsetting behaviour from him over the last 4 years?

Are all men secretly like this? I wonder if that explains wtf is wrong with them. Jeez they need something in their tea to calm the fuck down. It’s made me feel quite queasy, I can’t imagine how you cope every 3 days op. I’d never want the needy sex pest near me at all.

I didn’t say he definitely is, but it’s an extremely common trick of cheating men so it’s something to consider.

He's either been watching too much porn, or (as someone else said 👆) he's been reading stuff for gullible men from the Tate-osphere. (Or he's just magically turned into a bit of a dickhead)

I get pain in my balls if I don’t cum

I would dump his arse for that alone. He’s 42 ffs, not some horny teenager. I can’t help wondering if he is checking out of this relationship for whatever reason and is getting his excuse in- in this case that it’s all your fault for not having sex with him enough.

Well that's just ridiculous. You should want whatever he wants? Does that mean he should also want whatever you want? Does this apply at dinner time? "I want a cornflake and pickle sandwich so you should want one too, why isn't it ready?"

He has completely separated sex from mutual desire, and for him it has become 100% about his control, and your subservience. I would actually feel very unsafe in this situation, I can't read it as anything other than (incipiently) abusive.

I don't think this man respects you one tiny bit any longer. Hes been radicalised by some manosphere shite I expect. Perhaps you should report him to Prevent (only half joking...)

The fact he feels entitled to sex whenever he wants it is such a red flag and a turn off. Please think about whether he’s the one for you OP he sounds like a creep

It's weird that he's started doing this out of the blue though. Either he's been influenced in some way - manosphere, porn, influencers or whatever - or something else has changed. Like he's taking medication/drugs, maybe?

Although if he's WFH alone in the house, it's more likely to do with online content he's absorbing IMO.

My God, what have I just read?
I don't see any solution to this except ending the relationship.

It makes you responsible for his physical and emotional wellbeing. He cant take responsibility for himself (to have a wank) so its on you. And his manipulating you into acting how he wants to act. At the very least its extremely dysfunctional communication. He's not fussed about you and what you want is he? He just wants his needs met. Now.

Jesus christ throw that one back 🤮

He gets worse. Does he have any other conversation other than very bad sex talk?

Oaft he expects you.to be on duty !

It isn't. He's being needy and demanding and petulant. He's like an over-sexed toddler (and yes I apologise for that description).