I had a big drinking night at around 4w too (without knowing about the baby) and my baby's perfect, I think you need to be consistantly binge-drinking to have a major effect on the baby - remember, before you miss your period the baby's mostly living in the eggie, not even taking stuff from your body, so you and the baby should be OK. OK, so my big drink was just the one bottle of wine, but I don't get hangovers so don't know if it's comparable.

For the first month of pregnancy - the first two weeks you haven't yet ovulated, the next 10 days the baby is an zygote and hasn't implanted in your uterus, then you have four days in which the baby snuggles in and starts to make a placenta before you miss your period; this starts to comandeer your body, taking nutrients and making you up your hormone doses. But it does take quite a while for this to be fully in place - it takes 10w (from first developing) for the placenta to be able to be the fully gung-ho thing that we assume it is from the start.

Current guidelines say you can still have one unit of alcohol a day and it not affect your child, but it sounds like you've given up alcohol anyway. It's an on-going thing, so the odd glass won't affect the baby, but constantly going out on the razz will.