I am having same problem. I was taking nexium 40 mg more the week now. I did have my periods, due on 25 th of this month. We didnt have unprotected sexual activity.
I am surprised to find so many comments about the same problem. I am having similar difficulties, but thought my irregular cycles were a sign of menopause on its way. I didn't make the connection to the nexium even though I have been taking 80 mg for the last few months and 40 mg for several months before that. I also have dizziness, lightheadedness and higher than usual blood pressure at times, but blamed it on baclofen or trazodone that I take for esophageal spasms and a cough. Maybe it's all because of the nexium. I haven't even bothered to mention it to the dr.