Originally Posted by Engine

Far be it from me to give give dating advice but in the case of internet "hookups", an emotional affair is what's being had.

However, I think the OP made a point (more than once) to say that his current physical relationship is established as casual, uncommitted, and not monogamous. So.. why would his "internet hookup" be any worse than him dating multiple people in real life? That's pretty normal for humans.

I'm confused about why people presume that the real-life girl expects monogamy. OP said expressly that she does not. If she does then, yeah, I agree with the "you're a sleazy douche" comments but he claims that she does not. If in doubt, he should talk to real-life girl about it and accept the consequences, as has already been said.