How to bring back passion

I'm not sure if this belongs here or in the relationship section. It seems to me better here? but if not feel free to move it.

Anyway, I have been in a relationship for 4.5 years. For the past 3.5 years, it has been an utterly passionless relationship. She has completely lost all passion for 3.5 years. During that time, sex has happened maybe 3 times? maybe only 2? I honestly don't even remember. There is no passionate kissing, no sensual caressing of bodies, nothing like that. Hugs, hand-holding, pecks on the lips and such are very frequent, however. Just no sex, nothing sexual, nothing that has even the most remote possibility to lead to anything sexual. She has no passion.

Lately that has been resolved by me having sex with other people with her knowledge. She would prefer I not have sex with other people, but I don't hide it from her, and she has accepted it as part of our relationship.

But I'm tired of that arrangement. As strange as it may seem to some guys who might dream about such a situation, I want it to stop and have a sexually monogamous relationship with my girlfriend. Having an endless string of loveless sexual encounters with random women I don't even know while maintaining a sexless love in my relationship has become a situation I can no longer deal with. I need passion, but she is unable to give it.

Then I left her and moved out. I couldn't take it and felt I needed to move on. But she kept calling me and begging me to come back, and the fact is I do love her tremendously, so I did after only a couple days living in a motel. I came back tonight. We talked and she promised to try to work on her lack of passion. but how?

That's my question in this post? How does one attempt to regain passion when they have lost it? She once had it. We were very passionate in the early stages of the relationship. She is clearly capable of passion. neither of us know what steps we should take to try to help her regain the passion even now that she has promised that she is willing to try. A person obviously can't just decide to feel something they don't feel.

and before anyone brings it up, therapy is not an option. She completely refuses to go first of all. But even if that were solved, we live in Korea where mental health is not taken seriously. There are therapists but they are way out of our price range and the health care system covers none of it.

Thanks for any help. I know this was a pretty long post but wanted to give all the background.