I am 6 days late on my period. Have suddenly gotten severe lower back pain along with stomach pain. Yes sexually active. No birth control. Any ideas.

Period coming. It is possible that your period is coming, and often with a late period the bleeding and cramping is worse than usual. The pain may be from the period coming. It is also possible you have a cyst on an ovary. Pregnancy is possible so you might want to check a pregnancy test. If positive you might have a tubal pregnancy so get it checked.