I haven't started my monthly period yet,iv got brown sticky discharge,iv been having unprotected sex with my boyfriend for a while but i'm on the pill?

Infection (STI): If you are taking birth control pills (BCP) every day for more than a month, then it is unlikely that you are pregnant. Woman taking BCP usually have very regular periods, so something is amiss. Unprotected sex greatly increases the likelihood of acquiring a sexually transmitted infection (STI). Use of condoms is the best protection from STI, including HIV. You should be tested for STI.