Can alcohol impact the embryo during the 3rd week(1 week after conception)? if so, how? wouldn't it just impact implantation? didn't know and worried.

No effect likely: There has most likely been no damage done to the baby from early alcohol consumption. Here is an interesting study from last year: http://www.health.harvard.edu/blog/study-no-connection-between-drinking-alcohol-early-in-pregnancy-and-birth-problems-201309106667 Avoiding alcohol during pregnancy is the only way to be sure to prevent even the possibility of Fetal Alcohol Syndrome.