Drank in 1st tri

Okay so, my estimated date of conception is October 9- and I read that FAS affects the baby's facial features most on the 20th and 21st days of pregnancy- I know that I drank heavily on Halloween weekend, (before I knew I was pregnant, obviously). I have not drank since I found out at about 8 weeks, but now I'm freaking out... Anyone know anything more than i do about these studies???