Gender

We had our ultrasound on Friday and they told us it a girl I am super excited. I started sorting through my son's clothes to sell and my cousin said what if you sell them and then you have a boy now I am so scared to do anything what are the chances they could be wrong. The picture sure looked like a girl and I just feel like it's a girl. I compared my son's ultrasound pic to this one and they are totally different. I am so paranoid.