pregnancy test?

how long should I wait to take a try? I was supposed to get my period on Saturday but haven't yet. I'm never late, ever and on top of it I've been super nauseous al weekend and today. and it's not getting better. Imy boobs have also been super sore but they feel just as sore as they are when I get my period. I just am not sure if the symptoms of pregnancy can start THAT early.