@djh590, I can relate to a lot of what you are feeling. When my fiancee and I have sex, i do sometimes think about porn, whether it's other women or a certain act. Usually I can bring myself back to the moment, but sometimes I don't and I do feel guilty about it. I've noticed too that I'm more likely to look up porn after having sex with her, most likely over the next few days. Or if I masturbate to thoughts of other women, again, more likely to pmo.
That's helped me be aware that I need to focus on my fiancee if I'm having sex or masturbating, because the urges will be very strong after if not. One thing that helps me get back to the moment is touch - it's one of my love languages. The touch of a human or touching her is something that pmo can never provide. It does allow me to enjoy foreplay/sex more plus it feels more intimate and real. And I'd say don't focus on her/your private parts because that can build a sexual tension, the same way edging does. I hope this makes sense and helps in some way.