FAM/charting only - does it work?

Britney
Is there anyone here who is relying on charting their cycle as their only means of birth control (besides condoms on those fertile days). 
I'm getting married next week, and I'm a virgin. We want to wait a few years before having kids, but want to do it the natural way.
However, I'm staying with a couplr until the wedding, and they tried FAM and got pregnant after 3 months. :-/
Thoughts? 

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