What Causes Rust Colored Vaginal Discharge After Having Protected Sex?

i am 23 years old. sexually active with one partner for over 2 years. not on any kind of hormonal birth control. condom use every time. i have experienced this before but just want to check up on it. my last period ended the weekend of july fourth. starting saturday, i've been having a small amount of rust colored, somewhat clumpy blood or discharge. i have no pain associated with it. no moodiness, no other sympotoms at all.