I think of my girlfriend when I'm watching pornstars/models. For real.
I do sometimes think about other girls when I'm pleasing myself, because we'd all like a little variety. But when I'm with my girl, it's all about her.
you should be 100% focused on her and her needs. If your bored enough with her to imagine another woman during sex you need to stop using her for her body and end that relationship. but what do I know I'm single :dunno:
**to add a side note:
I'm usually to into the moment when I'm with my guy to think about anyone else.. It's like when it starts to get 'hot and heavy' my main focus is on him and how to make him happy.. Make sense?