I switched from aviane to vienva in february and now havent had my period for the last two months. i am not pregnant. i have gotten some signs such as backpain, but no blood....

Possible reasons: Might be related to med change.Reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; Over-exercising (endurance athletics), stress, travel, significant illnesses, oral contraceptives & other meds, Illegal drug use, breast feeding, hormone imbalances and medical problems (i.e., PCOS). Pregnancy is #1 reason.