Spotting: Period or Pregnant?

Yesterday was the day I should have started my cycle, I’ve always had one like clockwork every month since I was 10 years old. The first two days are always really heavy and I have really bad cramps. Yesterday I woke up with cramps but I’m not bleeding as heavy as I normally would. What are the chances that this is normal vs the chances that I could be pregnant? I’m definitely going to take a test, I just want a little info so I know if I should be worried or not.