Early signs of pregnancy?

I made a mistake about a week and a half ago and had unprotected sex. He intended to pull out, but I don't think he pulled out quick enough. My period isn't supposed to start for a few days, so it's a little early to take a test. I rarely ever get menstrual cramps, but I've had really mild cramps yesterday and today, yet no start of my period. I'm pretty nauseous, and I have a terrible migraine. My breasts are kind of sensitive and I'm peeing a lot. Is it possible to experience symptoms this soon after possible conception, or could the symptoms be something else??