kiki, I try to look at it the exact same way ROOT described. He is MY H. Not the OW's. She has NO right to him but I do.. Also, the lack of ML was a HUGE problem in my marriage as well. What caused it?? Hopefully, we'll get to work on that some day in MC. In the meantime, I now know how important ML is to my H and it seems like every day we grow closer. I am certain that part of the reason is because of the fantastic sex life we are now experiencing.
I also got some great advice from ROOT. Make yourself as attractive as you can. Buy some great lingerie. Flirt a little bit. Boost your confidence by being the hottest woman he knows!!!
As for feeling used - enjoy it yourself; maybe you are "using" him for your pleasure - ha!