Backstory (tw: baby loss)

Back in May I delivered at 18wks, my cervix was ruled incompetent. They never ran any test or anything to see what caused it. They gave me the ok to start back trying in August. I had a cerclage placed at 17wks. Well here I am 20wks I had my anatomy scan ( I honestly hate when students do anything pertaining to my appointments I just feel they miss things) anyways I had the scan and they told me baby looked fine. They never once checked my fluid, nor checked my cervix, and only did one scan of the spine, 20 scans of the heart, and 3 of the brain. Told me I don’t come back for an ultrasound until February. I’ve been doing every two week US for the last two months. Just curious on how this is even accurate to stop the US that long considering I’m high risk with a history of preterm labor