With my first pregnancy I was drinking for the first 6-8 weeks, as I didn't know I was pregnant. I always had irregular periods and was still spotting occasionally. While I was worried about FAS, once I got the PG test result of +, I was able to easily quit. My son will be 14 soon and besides a little impulsiveness, he is perfect!
The other two pregnancies I knew immediately that I was pregnant without even taking a test.
Keep "Not Drinking" and try not to worry.