I'm 3 days late of my period. I'm usually on time though. I took a pregnancy test but it came back negative. Could I still be pregnant?

Maybe. If the pregnancy test was a reliable brand and done properly at three days after the missed period you are not likely pregnant, but you should check again to be sure. There are lots of things that can delay a period - such as worrying about whether or not you are pregnant! if you are not trying to get pregnant please use some safe method.