OP consider taking a break. I’m sure she is probably bored fukking the same dude too. That’s not a dig at your sex game. That’s just saying she’s human too and we all get tired of the same thing all the time.
If it’s purely sexual, is the quality of your sex with her pretty good? If so, it might just be the monotony. Try building sexual tension. Give each other a challenge to not fukk for a certain time period while still teasing each other.
If it’s just the lure and excitement of a new sexual encounter, avoid the drama and take a break. One of the reasons women react so badly to cheating is b/c it’s one-sided. We end up making sacrifices in our sexual and emotional needs for someone who isn’t doing the same for us, when we could be getting sexual satisfaction as well.
Which is something all humans deserve and need. So take a break. Hit that Donnell Jones “Where I Wanna Be”. But if you truly care about her and not just operating in ego and possessiveness, let her go during this break to explore her needs too. Nobody should be alone in a relationship while you doing you.
If the love is strong, ya’ll will come back to each other. If not, that’s life and you move on.