Missed Birth Control , Breakthrough bleeding , cramps , sex

Breakthrough bleeding occurs when estrogen levels in the body drop- this affects the endometrial lining in your uterus and results in breakthrough bleeding. Breakthrough bleeding that occurs after three missed pills is similar to withdrawal bleeding and caused by consistently low levels of hormones contained in the birth control pills. (This is also what causes "periods" at the end of the pill pack, and can be accompanied by cramping.)

This does not mean that you're pregnant. but it's also NOT a sign you're not. Although spotting and one-sided cramps, about 6-10 days after unprotected sex may be a sign of implantation, these implantation cramps will typically last 1-3 days. Withdrawal bleeding and cramps should subside after you have steady levels of birth control pill hormones in your system, and should subside within a week. If you have signs of pregnancy, such as nausea/morning sickness, tender breasts, or sudden weight gain, you should schedule an appointment with your doctor.

(I'm currently a few days past missed pills and experiencing breakthrough bleeding too.)  Hope you feel better. It's just caused by your body reacting to not taking the pills, and it should resolve itself in a few days to a week. If you're still having problems, get in touch with your doctor.