Any use of the Pill is cooperation in the evil of providing the Pill to society at large. A consistent person would not wish to entangle themselves with a device whoe normal use they oppose. You might not be aborting anyone yourself, but by helping make the use of the pill very widespread and acceptable, you indirectly are.
Perhaps we should boycott the manufacturers? There's McNeil, of course they also make Tylemol, Motrin, Floxin, etc. And there's Wyeth who makes Premarin. But then they also make Advil, Centrum, and Chapstick, etc. So every time someone purchases one of these products they are supporting the manufacturer of the Pill and other birth control devices. After all, why would you support someone who makes birth control pills? You don't, do you?
If I keep a gun for self-defense, am I contributing to make guns widespread and available for those who wish to use them for murder?