6 months without a period?

I'm 14 almost 15 and I've had a period science I was 11 and they've alway been very irregular, never 2 months in a row. And always VERY light for 3-4 days. But now I havent had a period in 6 almost 7 months. I'm starting to get worried because of my very extensive family history of Ovarian diseases, I was diagnosesd with large cysts on both ovaries on my 13 birthday... Is it normal to be this irregular.??