Ultrasound concerns, FTM

My husband is military and we're stationed in Hawaii so we don't have many healthcare options. I'm 6 weeks along and have a much younger sister (8 years) who has rare genetic disorders. My mom was high risk or her next pregnancy as well, bc of the issues I listed above. My provider told me that I'm only getting 1 ultrasound throughout my whole pregnancy, and that will be at 20 weeks. Is there any way that due to my sisters multiple disabilities I can get more ultrasounds to check up on my baby? Freaking out! Have another appt on Wednesday, so will ask then. Just wanted input