Pregnacare Conception Tablets

I am 35 and a first timer at TTC and first time taking the Pregnacare Conception Tablets.

So I started taking the tablets half way in to my 28 day cycle and I have now been taking them for the last couple of months. My periods are usual like clock work but since I have been taking the Pregnacare my periods are all over the place. My period was due yesterday but still not shown. I have taken 3 test and they have all come back that I am NOT pregnant.

I have been reading the online reviews about the Pregnacare tablets and they can make your periods late. I don't understand why it would do this. Isn't that wrong for people like me thinking they are pregnant because a period is late and then couple of weeks later is shows. 

Soes anyone else out there have this same problem with the Pregnacare Conception tablets and what dontou think to them??