side effects of one a day prenatal with DHA and iron?

Amy • Enjoying life as a new parent to a baby girl
I started taking these about two months ago, and have noticed that I've had horrible constipation and cramps between ovulation and AF. Normally, I'm pretty regular, but did tend to notice about a week before AF it was a little harder to go (prior to prenatal vitamin). Anyone else have this issue and have advice?