Could I possibly be pregnant?

My boyfriend and I had sex for the first time this past Saturday (11/14/2009). It is now Tuesday (11/17/2009) and I'm not sure if what I'm feeling is apart of the earliest symptoms of pregnancy or what. I know a few days would seem almost impossible to tell but I've read website after website about different symptoms and reading that they could range anywhere from straight away to 6 weeks. Yesterday and today, I felt nausea (even as I type this, I feel like I could keel over at any moment), I've had some cramps (not too bad... I probably figured they would be from having sex anyway), my discharge has been kind of dark cream/light brown (I accounted this for just having sex, as well) and I am nowhere near my next period. This is all I can think that's been happening just within the past few days. Like I said, I know that since it's only been a few days, chances of telling if I am pregnant or not are slim but you never know, I guess. Help!