If I were in your situation (and I have been), I'd spend some time thinking about whether monogamy is important in a relationship for me (and I discovered it was). If it is, then you're with someone who does not respect that value and for whom it is not important in a relationship. That doesn't bode well for any future you two might have. You'll never trust her again and will always be suspicious.
If you two didn't have a monogamous relationship in the first place, you might want to talk to her, express your feelings about it and ask her if that's important to her.
And the configuration of your genitals has nothing to do with it. The issue is monogamy or the lack thereof. Don't turn it back on yourself, it's all her choice to do that.
It would be a deal-breaker for me, but it's your decision.
Dennis