well it's also true in the very beginning of a sexual relationship that it usually gets better as time goes by and you have more sex. maybe you two(actually it sounds like her) aren't totally comfortable with each other in the sack yet and so it's making things kind of blah. give it some more time and see if it gets any better. if not, leave her and tell her it's because she's horrible in bed, her ass is too big, and she burned dinner one too many times.
other than that...let's get down to the source of the problem. she's not going down on that hogg of yours is she. don't lie. have you tried pushing her head down there with your foot? how about when she's sleeping have you tried putting your stick in her mouth and whispering in her ear that it's chocolate and that chocolate is yummy and delicious? this has always worked for me. are you going down on her? is she having trouble finding a decent channel to leave the tv on while you're hitting it from behind?
expand so we can help.