ditto on the thyroid check, though keep in mind levels can fluctuate, so your test might show normal, but it can still be a prob & vice versa.
other than that, you can ensure you eat a very nutritious diet and supplement a B complex vitamin (the B6 is key though the complex is important). other supplements to try - in reverse order of reco - are evening primrose oil, fish oil (a really good-quality one like salmon oil and NOT cod liver oil), maca, and last-but-certainly-not-least, vitex (chasteberry, chaste tree).
if you do fall preggo, it's a good idea to consult your healthcare provider about gradually weaning off any supplements you take once you get well into the pregnancy (after 10-12 wks or so).
p.s. a great resource = "Taking Charge of Your Fertility" by Toni Weschler
edited to add: You got it -- Taking Charge of Your Fertility is a really really great resource for anyone seeking to know more about how to optimize her health with regard to her distinctive physiology as a woman. Sorry I wasn't clear, and the warning about weaning off maca or vitex supplements if you fall preggo is a valid one *just in case!* (My nephew is one of those "1% babies" so, though we are very grateful "there is he," we know it can happen sometimes at the most *interesting* times, let's just say...)
Good Luck! ;D