Possibly pregnant?

My boyfriend (18) and I (17) have had sex 4 times since my last period and he ejaculated each time. We didn't use any method of birth control. My AF was due yesterday, and still hasn't arrived. I've had mild nausea, bloating and what appears to be spotting, but I haven't experienced sore breasts or any of the other telltale signs of early pregnancy. Should I take a pregnancy test? Or are my symptoms more along the lines of PMS?