Just thought I'd mention this in case anyone has had similar problems...
I went off the pill in October 2013, had a normal period for three months then nothing for over a year. At first I thought I was pregnant but every test said no.
I saw three different doctors who basically told me they didn't know why my periods stopped. I had hormone tests, internal ultrasounds and everything was fine.
I then started seeing a nutritionist on the suggestion of a friend who said my zinc was low.
I know this is connected, but although I felt better and had spotting, I still didn't have a proper period.
Finally, I went COMPLETELY off sugar. Since then I have had three periods between 26 to 28 days and am now five weeks pregnant for the first time ever!
Not trying to say this is the answer to everything but I think it made a difference for me and there was so little around on the internet about my particular problem I thought I'd share.
I've also cut out a lot of carbs.