First thing you gotta learn is that the vast majority of women are a waste of fucking time, energy and money. I guess after you are in enough failed relationships you will come to that conclusion. It's not that all women are a waste of time, energy and money, it's just that MOST are. Most women, I wouldn't give the time of day. My desire for pussy is far less than my hatred for dealing with the BS that usually comes with getting that pussy. I'm usually trying to hand the pussy off to someone else, because I don't want to deal with the BS.
Currently, I am seeing a woman who has money. A couple times a week she invites me over to her nice house, feeds me, let's me get in her hot tub, play some Xbox One and I give it to her like a stud horse. Then, I leave and she doesn't bother me until she wants me to come over again.
I think she may be seeing another guy as well... But, I really don't fucking care. This is the most hassle free woman I have found in a long time and I'm enjoying it.
So. My advice to you. Just stop caring. Don't break up with her, because then you ruin any chance at getting that pussy. Just, stop worrying about her. Do your own thing, try to meet some other chicks, keep talking to her every now and then, but don't sweat it. Who cares if she's banging other dudes? Are you trying to marry this chick or do you just want to get your dick wet? Put a little space between the two of you, so maybe she starts wondering what YOU are doing. Then maybe she'll throw that pussy at you, because she's afraid you're looking elsewhere.