What Causes Spotting After Taking Placebo Pills?

Hi, I am on birth control. I take it diligently and never skip. My period came 3 days early last month and was normal and I continued Into the placebo pill with no problems. This month it started 4 days early, it was heavier than it has been but nothing to unordinary, but now I am on the placebo pills and I am starting to spot again and feeling symptoms of another period. Does this mean it s not working anymore or something else