possible pregnancy?

My boyfriend and I are trying to conceive. Last month, we had unprotected sex during my fertile time. About a week later, I noticed my breasts were very sore, and I am more tired than usual. I thought maybe I could be pregnant, but I would wait to take a test. A few days after my period was expected to come (my cycle is always regular), I started bleeding. So, I figured I was getting my period, it was just a few days late. But it only lasted for 2 days, not the normal 5 days. My breasts are still really sore. And this morning, I woke up nauseated. I threw up, and am feeling better. If I wasn't at work, I would go take a test, but I am just curious if I could even be pregnant, because of the bleeding?