Help, could I be pregnant?

A couple of days ago I got sick with bronchitis, which is now clearing up. When I was sick I got really lightheaded and proceeded to throw up a few times, when I did I just thought that it was because I was sick so I didn't think nothing of it, but I tested anyways and it was negative I was fine for a couple of more days no sickness, last night I started feeling queasy and lightheaded after I smoked a cigarette, a couple of hours later I ate a bacon sandwich, and I felt sick to my stomach but I never did throw up, when I woke up this morning I threw up the bacon sandwich. Could I be pregnant? I did have sex on some of my fertile days this month, and my period is supposed to be due in four days.