Am i pregnant?

Patient: The date of my last period was on the 8th of march.. I had sex on the 17th and i know for sure that i ovulated on the 20th of march.. My next coming period is supposed to be on the 4th of april.. I’ve passed out some brown spotting a week before my period is scheduled.. I took a pregnancy test yesterday which was 3 days before my coming period and the test was negative however i tend to feel weird with sore breasts. Could the spotting be a result to implantation? We have not planned to get pregnant and could an early abortion work?