I'm not exactly sure what else it could be. Your doctor would be able to tell you better than any of us.
But I have a sneaking suspicion that you are pregnant. Especially since you have been forgetting to take your pills. My best friend has a beautiful 3 month old son, but he was the result of her forgetting to take her pills regularly.
If I were you, I would take a pregnancy test and go from there. If it comes out negative, call a doctor. It could be that your system is out of balance with you missing your pills. Or it could be something else, but I have no clue.