Bleeding inbetween periods?

I am on the Pill and due to this (and have been since I started 8 years ago) I am regular as clockwork. However, for the first time ever I have noticed I am having the same sort of discharge you have at the very end of your period. I have recently started dieting and exercising (jogging 20 mins a day) to lose some weight, could the two be connected? I am ually active and never been pregnant!