So confused- should I take a pregnancy test!? Need advice! ?

Me and boyfriend have just decided to start trying for a baby, my last period started on 23/05/11 and as I have a 21 day cycle I was supposed to be on my period by the Monday just gone 13/06/11 however i still haven't, my breasts are sore, and been having very bad back aches and occasional stomach ache and headache, I'm also feeling very tierd, however I could be just wishful thinking and my period could come, anyway I was thinking of doing a pregnancy test tomorrow or would that be too early? Please help many thanks in advance xx