What is the difference cramp between early pregnancy vs pms?

Hindsight. The only reliable differentiation is a positive pregnancy test. Every period is different and every pregnancy is different. A lot of times you will be able to tell in hindsight that your pregnancy symptoms were pregnancy and not pms, the distinction can be very subtle, but it can be obvious too. If you are trying to get pregnant or not trying the wait is excruciating. Best wishes either way.