Aimz, I'm sure you may have read my recent diagnosis - hopefully part of your BT will be tested for thyroid levels.
When the dr started asking me of I had any heart palpitations, hair loss, very light or scant periods, weight loss, shortness of breath, dizziness, fatigue around middle of the day. I said I had all of these, but I thought they may have been 'normal' after the pregnancy. Turns out I've have a hyper thyroid.
Hypo thyroid sounds similar but weight gain, and both these conditions can effect ovulation, length and heaviness of periods.
Just ask your GP, if she hasn't done it already to check your thyroid levels.

Good luck, hopefully it's just coming off the pill!