I am on loestren 24 the bc pill, well i'm in the middle of my pack so i shouldn't be bleeding, my fianc and i just had sex and i started bleeding why?

Various reasons: Bleeding associated with intercourse can have various causes, most of them not serious. These range from cervicitis (infection or inflammation of the cervix), to cervical polyps (most are benign), to breakthrough bleeding (from too low dosage a birth control pill), to uterine polyps (less common but still benign in most cases). There's no need for panic but it would be best to see your doctor.