Worried about early period.

So my period wasnt meant to be due today, it was meant to be five days from now, however Im having quite strong cramps but very little blood. I attempted to have sex on the 27th but we were interupted however their was penetration and obviously a condom was used, we checked the condom after for any rips or tears and it was fine. But I am a little worried that I am having my period but my breasts havent swelled up.