id leave man, as much as its horrible, you are not a bad person if you leave, you have needs, wants, desires. you have valiantly tried to help her and be there for her. but you can’t help the fact your relationship is dead. you can’t keep pressuring yourself into something that is emotionally unhealthy for you as well. I honestly can’t see a better option in this situation than leaving or talking to her about you being able to sleep with other people to fulfil your need for physical intimacy
There are so many other ways to be intimate other than sex with your partner. Do you cuddle, kiss, hold hands etc? I completely understand your desire for sex but perhaps you can get the intimacy you desire in other ways too until she’s ready? I would also absolutely recommend couples counselling as well though. You’ve been an amazingly supportive partner for 2 years and if you feel you can’t do it anymore, that’s perfectly valid.
You can bring it up. You can tell her that you need to start discussing the physical intimacy in your relationship without telling her “I need sex or I’m gone.” Starting the conversation is not the same as pressuring her to do it. You need to find out where she stands on sex in her life.