Please answer.......?

I drank heavily for the first 3 months of pregnancy and I have been very nervous about having a baby with problems due to my consumption. I had my 20 week fetal abnormality scan and everything came back perfect. The baby was actually bigger than the average and there was no problems with the heart or size of the brain. My question is... can the results of that u/s guarantee that the baby was not affected too much from the alcohol exposure? Although I am very excited to expand my family I just don't feel that I can really enjoy my pregnancy because of the constant worry. Ps- serious answers only and no, I did not know I was pregnant while I was drinking. Thank you everyone...