I am 18 years old, haven't missed my period yet, could I still be pregnant?

I am a successful, driven private university business student going full time at school. My boyfriend of one year is in the same situation, although he is at a different college. Well, last weekend I went to visit him, and the deed went down. However, we used a condom (that did not break or completely slip off) and he pulled out, so it seems like a statistical improbability that I could be pregnant. But me being paranoid, I have looked up all sorts of things about early pregnancy symptoms and how they can come on at like 8 days after the . Scary thing? It started this morning-- the 7th day. I felt mild cramping when I woke up. Keep in mind that I am also due for my period in the next few days. But it seems like symptoms just keep randomly popping up. I have felt bloated, but found out that was due to minor stomach problems. My temperature seems up, but I was also out in the sun for a while today and yesterday. I have had cramping, but I usually do when PMSing. I am very confused-- and scared, like terrified scared. Scared to death scared. If this were to happen, it would thoroughly ruin my future, the one I have worked so very hard for, the one I have dreamed my entire life about. So perhaps my "symptoms" could be due to my paranoia. I am not sure. Anyone have opinions/ info to offer? I heard that nausea doesn't set in until the 2nd week after conception, which leads me to believe that most of this is in my head, but one can never be sure.