Period or pregnant

I was supposed to start my period Monday, instead I ended up starting Sunday. Now that's nothing strange, sometimes I start a day early or a day late, but it's normally really heavy. My last period was normal and heavy like always but this one is strange to me. So I started on Sunday with a normal flow, then yesterday it was a little on the medium side, and now today I'm barely spotting. My periods usually last 4-5 days, weird question but could I be pregnant?