Confronting him isn’t an option. He would never forgive me looking at his phone.
You've caught him out and so he's worthy of the bin. What he did was far worse than you looking at his phone. He would've shagged the other girl if she hadn't said she wasn't up for it.
The sex is good and I give him attention, I don’t know why he would want something from someone else.
Sleazy men are sleazy men. Some men are obsessed with sex. There is little limit to the amount of sex these guys want in my experience. They don't just want one sweet (you.) They want a bottomless bag of pick and mix. It's the ego boost as much as anything else. It's not solely a physical desire for them- it's a psychological need to conquer, ego boost and novelty.
Contrary to what it sounds I know he does ‘care about me’. He can be very attentive and thoughtful.
That's what they do to keep you sweet and keep getting the sex and attention they want. You can never know how much of this 'care' is a lie to get what he wants so it means nothing. You cannot trust him.
You could get a guy who is better than this in a week or something (but you should start actually following the law and stay 2m apart for now, assuming that's the law where you are.) It'd be away of getting a decent one. This one you've got is not a good guy- he's treating you badly.
When lockdown's relaxed eventually, you know that you could get a bloke off Fabswingers the same evening.