You may just need a break from the birth control for a while since you've been on it for so long.
That was one of my options when I went to the doc last. But I decided to go ahead and try a new pill instead of getting off of it and risk the chances of becoming pregnant. But if I still have problems with the new one, i'll be going off of it for a while. Sometimes your body needs a break to re-adjust to how it was.
Vitamins shouldn't affect bc or give you the pains. There's not too many meds out there that affect them. I take my vitamins everyday and have been since I was little and it has never caused any problems.
I'd say if you still have the problems a month from now, even if they have weakened and don't come around as often.. Make a doctor appointment. Let them run some test and they'll figure out what the culprit is. =)