My girlfriend currently has a similar situation as yourself at the moment. For a very long time she was on the Pill and a few months ago she started having periods altogether. Sometimes the doctor will suggest that you have a break so things returned to normal. That you can change the Pill if you wish as this is what my girlfriend did and the cycle is back to normal. Maybe your body just get used to it or something along those lines are not sure. In the long term of things I've never heard of it affecting anyone's fertility. I hope this is of some help to you.
Jez
http://www.onelifeboard.com - Discuss life, love, health and living. Get information and advice on topics that matter to you! Get support and enjoy lively conversations.