I don't understand why it won't tell you your fertile period even with a tubal ligation. Those things can reverse its self. It's unlikely but it happens and I'd like to know when to avoid sex because we always have unprotected sex. We've been together almost a year we have 6 kids between us both and although I'd love another baby we can't afford it. And there's quite a few people that gaff the same dr add me get pregnant after the tubal