Getting an ultrasound without a positive pregnancy test

Since my last miscarriage I have been so regular with my period, you could count the days of the month with it. I'm now 4 weeks late on my period, but with no positive test result. I want to cut out the middle man and just get an ultrasound, but my OBGYNs of the area cant approve it due to Covid-19. I'm afraid I'm having a cryptic pregnancy due to symptoms that have been lasting for months now, even when my "period" was still happening. I think an ultrasound will give me the truth, and I dont know how to advocate for myself in this situation. Any advice?