tiredness just come off pill or pregnant already?!

I stopped taking the pill on July 20th- had withdrawl bleed a few days after lasting a week. Around ovulation time I felt all the symptoms- cramps; very sore boobs; CM. I am feeling overwhelming tired now. Period 2 days late..Can you get pregnant this soon after coming off the pill???? Or is this tiredness more a symptom of stopping it? When is best to do a test? I feel that I surely cant have got pregnant this quickly? Has anyone else had this?