Well if you've been together for over a year, I would think you'd have strong communication with each other by now. Just bring it up with her very honestly and sincerely. Ask her if she's ever considered going on the pill, and why or why not. Tell her how you feel about it and just have an open and honest conversation with each other. If you've been together that long and are having sex, bringing our sexual topics in coversation shouldn't be too hard. 
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"The world is so exquisite with so much love and moral depth, that there is no reason to deceive ourselves with pretty stories for which there’s little good evidence. Far better it seems to me, in our vulnerability, is to look death in the eye and to be grateful every day for the brief but magnificent opportunity that life provides"
-Carl Sagan
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