Ultrasounds

I was just informed today I won't be getting another ultrasound till I'm almost due because I've already had 2 (on Medicaid) and the last one was at 15+5 where it was shown it was a girl but I just want to double check to be sure and don't have the $100 to just get a 4D one. I'm so stressed out because I'm scared we are gonna buy everything girl and then last minute find out it's a boy.