Agree with what the last poster said! It's not good to go that long without a period! My gyno said no more than 3 months at a time.
I have some herbal ideas that can help bring on a period. I haven't used them myself, but I'll put them here for you to try if you like. These are from the book, "Herbal Healing for Women", by Rosemary Gladstar.
Here's one to help it come:
2 parts pennyroyal *herb* (NOT THE OIL! THE OIL IS POISONOUS IF INGESTED!)
2 parts peppermint
1 part ginger
1/2 part yarrow
1/2 part mugwort
Some other suggestions, just for fun.
*Hang out with menstrating women. Their phermones can rub off.
*Wear red. (I wore a big red fuzzy sweater the day my period was supposed to start, and it came right on schedule! It could have been chance, but hey, it's fun to imagine.

)
*Rub a lil pennyroyal oil on your tummy. (Where your uterus and ovaries are.) I wouldn't reccomend using more than 2-3 drops. The author once used about a teaspoon, and her period came with a venegance! It's not safe to take that much. Your period is likely to be heavy anyway, after going that long without one.
Like I said, I've never used these, so I can't be a personal advocate for them. Use at your own risk! I hope they help.