Pregnant?

So my period isn't due for another week, but I've been so tired and moody lately and today when I went to pee I was spotting a little pink. My husband and I have safe sex always. But when my last period finished we were in the mood and did it without protection. We didn't think we could get pregnant doing it the day after my period finished. What could it be? I never spot a whole week before. We are really not TTC simply because we feel our 1 1/2 year still needs our full attention.