What Causes Period Like Bleeding Abruptly?

I have a question. I am 18 and i lost my virginity a week ago. Several days after I started bleeding as if I was on my period. My period wasn't supposed to come until a week or two later. What does this mean? Is this me getting my period early or is it something else? We used protection and everything went well. Also, what are the chances of me getting pregnant by only having him use a condom.