Ohhhh man! could I be pregnant?

I don't no what it is but lately I just keep throwing up, I can barely have a cig without feeling sick or actually throwing up, cant drink without throwing up, and just a few hours ago I had a couple co-codamol for a headache.. but alas found myself praying to the Porcelain god about half a hour later. Even feel sick to my stomach after eating certain foods (unfortunately that includes macdonald's, bad times) along with random unexplained sickness a couple times a day. My periods also 3 weeks late but that's not entirely that unusual for me, i dunno am i just abit ill or what? Some opinions much appreciated, thanks.