Been cramping and on and off since November 25th

On my birthday my fiancé and I had a slip up, I have been feeling nauseous and lower cramping. I did have my AF from December 2-5, but it was not heavy at all like it usually is(also late by 9 days). I still have been getting cramps here and there, today especially. Also, I have been getting heart burn from usual things I eat. Do you think I could be pregnant?!