Painful periods for prenatal vitamins?

I’m wondering if anyone else has experienced this. I’ve been taking Pregnacare Conception tablets for around 2/3 months now and since beginning them my periods have been delayed by a few days to a week each time which is really unusual for me. But the main thing that’s been an issue is I’m experiencing really really bad periods pain. I’ve always dealt with bad paid so for me to say it’s for even worse it’s horrible. It’s gets to the point I question going into hospital I’m in so much pain.

So I just wondering if this is normal and/or if anyone else has experienced anything like this taking them or any other prenatal vitamins?