Supposed to start period monday but havent. on birthcontrol. have cramps and lower back cramps. with yellow discharge. whay does this mean ?

Infection/pregnancy: It's not uncommon for hormonal contraceptives to make periods lighter or even cease altogether. However, the yellow discharge, cramps and lower back pain concern me. I don't want to alarm you, but you could have a vaginal or pelvic infection or POSSIBLY an ectopic pregnancy. No contraceptive method is 100% effective and few protect against infection. Make an appointment with your Gyno ASAP.