Hey, I had the same problem... I went to my doc and he told me the horomones in the particular pill i was taking wasn't strong enough, so i switched brands. Eventually the same thing was happening again while using the stronger pills so i gave up and quit taking them. I noticed with the stronger pills that the side effects were stronger. It is possible that you just need a stronger pill.

This can be common when first starting out the pill. It is recommended you take it for a few months to let your body adjust.

Is your bleeding the same as a period or lighter?

If you are concerned at all, you can always call your doctor.

That happened to my while i was on Alesse. I was bleeding everday, enough that I was using tampons and feeling lightheaded.
I went to my doctor and he perscribed be Marvelon, which is stronger and the bleeding stopped. However, I find that if I don't take the pills around the same time everyday, I can start spotting again.
Are you taking your pills at the same time?