What Causes Pain In Ovarian Area?

Ironically, I have a BS in Human Physiology, but I cannot find any reason for the intense pain i am feeling in my left side ovarian area. I have been using NuvaRing as birth control for the last 3 years and have never felt something like this. I am 23 and have never had any abnormal paps or ob/gyn exams. Obviously going to a doctor is recommended, but I would love to have some options for diagnoses... I have no fever, no nausea, no headache, and no digestive symptoms... I just feel like I got stabbed in the left ovary. Help? Please?