Boy ? Or Girl ?

So I had my ultrasound at 19 weeks and I was given an envelope in which I thought would bring the ultrasound picture that shows it’s a boy or girl but it was just a paper saying it was a boy. I have a strong gut feeling that I’m having a girl. I have a 4 year old boy and I did great with him (during pregnancy) but with this baby I am completely exhausted and nauseous I was very nauseous and threw up quiet a bit in the first few months now I’m 20 weeks and still throw up once in a while. Could I just be wrong about my gut feeling?