Spotting while on the patch?

Sarah

I'm on the contraceptive patch for almost 6 months now and today is the first day of my patch-free week. Usually I take the patch off on Saturdays and then I start spotting/bleeding on Sundays, but this morning when I went to take my patch off I was already spotting. I'm not concerned or anything but this is the first time this has happened in 6 months. Could it mean I've used it incorrectly? And has it happened to you?