OK so the sex behaviour is in part because he doesn't care about your pleasure because he only cares about his own. And in part- so that you question yourself. It's having exactly the effect he wants it to. He wants you to worry that something about you isn't 'enough'. Or that you're doing something wrong.
It's all part of the overall act of making you feel like shit. Of devaluing you.
Think about it, sex with a partner is meant to make you feel closer to them. It's an opportunity to bond and show love. But at such a vulnerable time...he uses it to show you unkindness, disregard and contempt and make you feel less like a connected person and more like an object for his use. It's just horrible behaviour.
I'm glad you're starting to see.
Be aware that upon break up, he will try many tactics to con you back. And if he still has access to texting you ext when he finally realises you are done you will likely get anl barage of abuse such as 'no other man would put up with you'. So I'd suggest blocking after you've let him know it's over and told him not to contact you further.
(Read up on the narcissists hoovering tactics online and you'll see many examples of things he might do).
If you do this by text, screenshot the text once it shows as 'seen' and then block. That way, worst case scenario, if he harasses you in future and its ongoing, you can go to the police and show them you told him clearly to leave you alone.
You may want to allow a few replies from him before blocking just so he feels he's had the last word and 'won'.
If you have things of his, maybe get them back to him before dumping him or he will use them to keep contacting you. Alternatively you could post them to him (recorded delivery so he can't claim he never got them) or drop them with his parents if that's an option
If you must break up in person, take his stuff along and break.up in a busy, public place. Do not allow him to follow you home.
Consider changing your locks if he could have a key and changing passwords on your devices.
Once it's done, I recommend doctor ramani on YouTubes videos about narcissists. I say 'once it's done' because knowing about narcissists before getting out, can make us want to be like 'I know what you're doing, I see what you are now, you're a narcissist' and they turn that shit round on you. So end it first and then start learning all you can to help you keep him gone and help you to spot these assholes early in future so you never end up in similar situations again..