My period still hasn't came and I've been on the nuvaring for 4 months. Something wrong?

Perhaps not. As with birth control pills, some women may not have the withdrawal bleeding on occasion. This is due to the fact that NuvaRing contains both estrogen and progestin. Estrogen makes the uterine lining grow whereas the progestin makes it thinner. Progestin always dominates so most women will experience lighter periods. Sometimes the lining becomes so thin that no withdrawal bleeding occurs.