Pregnancy symptoms?

I finished my period early last week, then proceeded to have unprotected sex about two days later. I'm unsure as to how early one can experience pregnancy symptoms, but I have been having cramps, bloating, headaches, mood swings, fatigue, and a frequent need to use the restroom these past couple of days. My bbt is lower than usual, however. Considering I've recently finished my period, I'm curious as to what is causing these symptoms. Sickness, or possible pregnancy? Perhaps an irregular period? Thanks in advance for your input.