Alcohol during pregnancy

Hi I want to ask something , I get to know I was pregnant in December 2017 my 6 weeks was going on before that I was on my vacation with my hubby we partied a lot and had alcohol also (i m not a heavy drinker before marriage I don’t use to drink also but after marriage occasionally I started drinking ) but when I was on my vacation i had hard but when I get to know I stop having alcohol yesterday I was reading in a pregnancy book alcohol in 1st trimester can cause Fetal alcohol syndrome now I am very worried will harm my unborn beachside I can’t discus it with my doctor because In very visit my mother in law goes with me I’m very scared please mom reply me now I am 24 weeks pregnant