If it make you feel any better, it probably won't but with my DD I went on a girl's weekend and had approximately 90 oz of beer in one night. I didn't know I was pregnant and was maybe 4 weeks along.
She's fine and I say she's so smart cos I drank so much unknowingly on that one night. :D
Then this time I was probably only 3 weeks pregnant, didn't know and went to dinner with my parents for my moms birthday and had 3 glasses of white zin.
In both pregnancies I've waited until later to indulge in a glass of wine or beer. I usually only do it once a week or so and with a big meal.
I wouldn't beat yourself up abut the drinking in early pregnancy and even if you have a small glass now, I think you will be okay. I read something..somewhere that on average it would take 8 drinks a day for it to effect the fetus. I don't remember my source on that, I think maybe one of Penny Simkin's child birthing books....