What is this?! **TMI pic**

Ok so I haven't had my period since August and I'm on the 4th day of my period week on bc. Tonight I notice this. I always get this at the end of my period and I have not even spotted since Nov 1st. I'm on day 146 of this cycle and I have a Dr appt on Monday but that's almost a week away and I am freaking out! Took hpts and all neg. Has this ever happened to anyone?