Had you not said what you said (on another thread) about the inability of your musician friends (males) to find suitable partners, I would have suggested that you try a relationship with a woman from your musician circles as another attempt at keeping your current relationship. Sex with random women in bars did not work out, but in general the gf was not super upset, nor changed her ways in response to your denouncing sex with random women, so maybe try a deeper relationship with somebody from your social circle? It would be, sort of, in-between what you want - meaningful monogamy - and what you did not like - sex with random women. A compromise.