Sex is a beautiful and essential act of intimacy in any committed relationship, so you're going to want to make it as awful as possible. Try to be as selfish as possible by finishing as quickly as you can and then playing madden in the next room immediately after. Assuming of course that this isn't already your normal sexual routine. If this still isn't working, try introducing unspeakable levels of kink to your otherwise vanilla sex life. Suggest incest roleplay, ideally while dressed as a teddy bear. She'll be yearning for a better lover in no time.