Which birth control pills decrease sex drive, which ones increase it, and which ones don't affect it?

Good question!: Oral contraceptive pills can decrease the circulating levels of testosterone in a woman's body--theoretically decreasing sex drive. Most women are not affected by this. The NuvaRing can also do the same, but to a lesser extent. Diaphragms, sponges, and iud's (intrauterine devices) would be much less likely to decrease sex drive. Talk to your doctor, sex drive is complicated. :-).

OCPs decrease libido: Combination oral contraceptives increase sex hormone binding globulin(shbg) in your blood. The increased shbg binds testosterone which can lower the libido. This can be overcome by taking a testosterone supplement intended for women. There are several testosterone supplements currently available, including less expensive generics.