Discharge on pill?! Anyone else?

So I know on certain birth controls your body builds sort of a “ mucus plug” type of thing. I was on it for a about a year and a half and then had to stop for surgery. When I stopped, the “ mucus plug “ had Come out. Sorta brownish tan and suuuuuuuuuper thick and stretchy. Now another year and a half later, since I’ve been on the pill my discharge has always been stretchy. But for the past two cycles, at the end of my withdrawal bleed, I’ll get this discharge that looks like the mucus plug.... why would that be coming out now when I’m starting the active pills back up? I take them on time and I’m not on any other meds? Is the pill not protecting me???