This situation probably wouldn't be so hard. She has a daughter from a previous marriage, that I treat and think of as my own.

Do any of you think, that it is "normal" to think sexual thoughts about a member of the opposite sex (or same sex), while in a loving relationship when your happy with the other partner? I'm not saying I do this all the time, probably about once a month. And it's not like I go out of my way to look at other women. My GF thinks that this isn't "normal" and that if two people are happy with each other, they wouldn't need to think about other people in a sexual way.

Have I cheated on her with watching porn so long ago? Do I cheat on her whenever I think about another woman sexually? Or his this a biological wiring that I have in my head? ie.. is it "normal"?