Unusually light period

I have had unprotected sex well really ever since I've been with my boyfriend, recently miscarried my son about 6 to 7 months ago we really aren't trying again but if it happens it happens and I always start on the 3rd of every month since I've miscarried and even before that my periods were already regular and i started 3 days before my usual date and i was having unprotected sex I've never had cramps like this time when i started i actually had to take something to calm it down and i stopped a few days later throughout the whole day i wasn't bleeding and then i started back up later that night very light though like spotting and usually my periods are kind heavy ,but this time it was very different very light hardly bleed any like usual ,could any one give me some explanation for it?COULD I BE PREGNANT???