Confused

Hi. So I was just wondering if anybody knows what could possibly be going on. Me and my boyfriend aren't trying to get pregnant but we haven't been not trying to not get pregnant either. Well yesterday I started spotting when my period was supposed to start and then today it was gone. I only used two tampons and there wasn't much on them. Well my period only lasted a day.... Normally my period will last for about four days. Has anyone else gone through this and know what could possibly be going on?