cramps: period or pregnant?

Hi guys. I'm was supposed to start my period today but I haven't. I have been having period like cramps for the past four days. I'm not sure what this means. Usually my period comes the day of or earlier. Did anyone else experience cramps in early pregnancy? I want to test, but don't want to get disappointed if it is negative. I might wait a few days and see if my period decides to come..