Could I be pregnant?

I had sex on July 3 , and have had a few early pregnancy symptoms (started about 1 1/2-2 weeks ago...tender breasts, nausea, frequent urination..etc.) I took a pregnancy test last week late afternoon, and it came out negative. My period (according to eve.) is suppose to come today. It did NOT come. Do you think it would be alright to test at the very end of the month, or should I test sooner?