A condom is equal to taking a shower with a rain coat on...what's the point? I know there are women who despise a man cumming in there mouths (lucky I never was with one) but for pre-cum to stop one from sucking dick is one I've never heard before. If she loves you 1/2 as much as you love her she should allow you to cum in her mouth. She can spit it out, although that's a turn off for me personally. If she doesn't swallow at least allow it to drool down your shaft with your cock in her mouth. She can brush her teeth afterwards.