Well, it's definitely possible. It sounds like that would've been right around the time you were ovulating. Having said that, you've got a 25% chance of conceiving with each ovulation, and your fertility reduces with smoking. Still, no way of knowing for another few days. Have you thought of buying a home pregnancy test to check? They're pretty effective these days.
In the meantime it'd be a good idea to stop drinking and smoking -- or try to reduce the smoking as much as you can, to reduce fetal exposure if you are pregnant. There are a huge amount of studies out now that suggest smoking is far worse for the baby than we'd ever thought before, so anything you can do to lessen that effect, the better... plus there are several agencies that really go out of their way to help pregnant women quit or cut back, so it's a good time to take advantage of that.
Plus, spinal cord formation happens over the next four days or so, so if you haven't already, take a little folic acid or prenatal vitamins. If you aren't pregnant, well, they're good for your health anyway so nothing lost there.