Period or what?

So girls I was supposed to start my period on the 25 I didn't start it until the 26 or so I thought it was a period it's really light like I don't even need to wear a pad just a little panty liner and it's not usually like this it's usually heavy and really dark red and sometimes even has clots in it I'm so Confused at what this could be bc this is so not normal for me any advise or suggestions would be greatly appreciated