Hi - Lots of information is available out there. Your milk will not necessarily dry up if your period returns naturally, but the pill often has a dry up effect because it manipulates your hormones. I don't know how open you are to alternatives, but there's some wonderful information available about fertility awareness that can be just as effective as the pill or barrier methods without any of the side effects of the pill or its counter-parts.
Look up Katie Singer - The Garden of Fertility, and Honoring Our Cycles - excellent, detailed resources about fertility - whether you're looking to avoid pregnancy or get pregnant - and there's special information about breastfeeding in The Garden of Fertility, too.
Also, to maintain milk supply, make sure you're getting enough high quality fats and proteins - real butter, fish oils, etc.. And enough sunshine on your face to have sufficient Vit D, too.
Good luck!