When should I take a test?

Alexis
My fiance and I had sex a few days before my last period, my period came and went. About 3 weeks ago my boobs got sensitive, I started feeling neauseous, and have been really exhausted. The last couple days I've had cramps. But idk if its my period or not. I'm suppose to get my period in a few days. When should I take a test with accurate results?