dumb question but

how do people know when their amniotic fluid is low? i haven’t had an ultrasound since 21 weeks and i won’t have another until 37 weeks because of the virus. my last appointment was at 32 weeks and the next isn’t until 37 weeks. i’m probably unnecessarily worrying but like is it something i should be aware of? i’m not leaking or anything, but i’ve seen people say they went in for ultrasounds and found out their fluid is low with no signs.