no periods...

I'm 21 years old and my husband and I have been trying to get pregnant for 2 years. My periods have always been sort of irregular but the older I've become the worse it has made me worry. I was taking birth controls at one time and my periods were regular I stopped taking them and they stopped coming ... haven't been to a doctor per day but a health department and they said nothing's wrong.. I don't have periods but maybe once every 6 months sometimes they come and sometimes they don't. What's wrong with me