His girlfriend is a fucking slut, which leads me to wonder:
-Why are you even halfway into her?
-Why have you not alerted your friend that his, BITCH! is hitting on you?
You say you're a cook? Personally I would have boiled her cunt in oil ages ago, you need to fucking NOT stand for this bullshit. Yesterday...
Obviously you know you've complicated matters by having been intimate with her, so doing the right thing at this point will cost you much more than it should've. Still, your honor as a man demands no less.