I'm on ovral l and my periods came on time but lighter than usual Can birth control pills cause lighter periods? I'm not pregnant I think as last sex 4 months ago and have had regular periods last 4 months just lighter and beta hcg test all negative all these months-less than 2 iu/l Just after starting birth control periods are lighter And I had done an ultrasound abdomen 2 months after sex Showed Empty uterine cavity.