It could be a number things. First things the pill does prevent the release of an egg from the ovaries. So if you didn't miss a pill then you should be fine pregnancy wise. However there is no 100% guarantee for any contraceptive unless its abstinence. If an egg did release then it usually releases 2 weeks after the first day of your last period. But seeming with the information you gave. -took the pill
-protective sex
- 1 1/2 weeks since the first day of your last period. And implantation bleeding usually happens 2 weeks or so after you ovulate you would have had to ovulate during your period.
I'd say it was some kind of infection. Do you have pain anywhere? If it continues you should go see your Dr.
Also if you did happen to miss a pill and you are ovulating sometimes you can bleed or have discharge when your ovaries release the egg.