Pain during sex- early pregnancy or period?

I had pain during sex yesterday. We tried different positions but missionary was the most tolerable. It felt like a sharp pain that went away quickly, in my lower abdomen. Also the other day I smoked a few cigarettes. But not one after another. N I also had Arby's 3 hrs before.. But I threw up 3 times. Idk if I got food poisoning or if the cigarette made me sick. It wasn't the first time i tried that kind. But it was the first time I threw up from smoking. (If that was the cause). N I felt so nauseous n I had a headache n I was dizzy. N the next day when I woke up I felt alil nauseous n my stomach kinda hurt. I haven't had those symptoms since then. Ive smoked since then but haven't thrown up. N the sides of my boobs have hurt n my nipples have been sore since the 3rd or 4th. Could it be because my period should be in a few days to a week? Or could I be pregnant? If I'm pregnant it would only be like 4 weeks.