In terms of physiological processes, pregnancy and premenstrual syndrome (PMS) could not be more different—one alerts you if an egg or zygote has been fertilized, while the other indicates your unfertilized egg is about to be released. Despite their differences, many people confuse early pregnancy symptoms with those commonly associated with PMS.

Hormonal causes

One reason the signs of these conditions are similar is because of hormone production. Progesterone, for example, is a reproductive hormone whose levels increase both during early pregnancy and the time right before your period. Because both things cause a spike in production, their subsequent physical manifestations show a lot of commonalities.

So how can I tell the difference?

The quickest and easiest way to tell the difference is to take a pregnancy test either at home or at a doctor's office. Some modern urine tests can detect pregnancy as early as four days