Cramps??

I've been on birth control for about 7 months now and I've taken pretty perfectly. But I started taking it at weird time on the pack I'm on now. I usually take it at 9:30 but I started this pack by taking it at 9:37. And for some reason this through my schedule off. I've taken in some nights at 10 and some nights at 9:50. I've been having cramps almost continuously in my overies and lower back but I'm 2 weeks away from my next period. I'm sexually active but my boyfriend has never finished. I've also started taking Vitamins for hair skin and nails, I don't know if that could effect it?? What could be causing these cramps?? It's scaring me