Right Ovary in Pain!

I'm 17 years old and have been experiencing severe abdominal pain on and off for about three days now. It's below and to the right of my belly button and is a really sharp pain, to the point that it is limiting my ability to carry out every day tasks. Iam sexually active and on birth control. Tri Cyclen Lo 28 3Phase Norgestimate-Ethinyl Estradiol. I am on the 10th day of my pill pack, and had my period when I was supposed to during the last week of my last pack. I started getting breakthrough bleeding on the fourth or fifth day of my pack and have had it since. It's the same amount as if not more bleeding than when I have my period. I want to assume that the pain is just because I'm continuing to take my pill while I have my pseudo period (five days of breakthrough bleeding?!) I'm not sure if I should be concerned about cysts or an sti or what. Really want this pain to go away. Also, I've had my period for about three years now and have only experienced menstrual cramps on one or two occasions, so I don't think it's severe cramps.