Pregnant or Mental?

So, I had sex with a guy friend 2 weekends ago, unprotected like a dummy... last Friday and today I'm noticing spotting, weird cramping, (the nausea might just be mental), and my mood has been horrid according to my co-worker. My period isn't due for another week.. Do you guys think I could be pregnant? I want to wait to take a test until I miss my period but I wanted opinions.