Going through a pregnancy test 3days after sex?

i had sex with my husband 3 days back..next days i felt cramps,spasm and fatigued which was not common sign for me..i mean this all bugged me for next two days..now at present my one breast hurts and aches nytime in the day..i went through home pregnancy test which came out negative..v had conception 4 days before the day of ovulation..so what is it??shud i think m nt pregnant or i have done test too early??i want to know as early...