As an alternative, rather than worrying about birth control, just tell hubby that he needs to lose 50 pounds, you no longer find those love handles attractive and why doesn't he look like George Clooney. That might just kill the mood. Then again, maybe not. :-))
The trial I was in also required to forms, not sure if birth control pills could be used. Or like OH said a condom.
To OH, thats funny!
The only reason I can think of that they want you to use two kinds of birth control is that if you became pregnant, the meds could cause birth defects.
I mention this only as food for thought.
Since you already have an IUD, how about condoms ? You could get the fun ribbed tickley ones. If you're gonna use them, might as well enjoy it.