Ultrasound

I’m 12 weeks pregnant according to my first ultrasound well I had another one and it showed me back a week ahead so I’m 13 weeks and 5 days but I go with the date from my first ultrasound 12 weeks 5 days I was wondering how soon can you see the gender clearly on the ultrasound because I have an appt in 3-4 weeks for another ultrasound to see the gender I will be probably 16 weeks pregnant 17 weeks pregnant if I go by my last ultrasound I feel like it’s still too soon to tell for sure has anyone had an ultrasound around the time and did the gender come out to be what the ultrasound said ...I just don’t want to start buying clothes and then the baby be the opposite sex thanks in advance