Heartbeat found super low in pelvis?

Okay so every visit to my OB has been great. But until after my anatomy scan my Dr only checks my BP, and baby heart rate. Well I'm 20 weeks and my last appt was 2 weeks ago. Every time he finds baby's heart rate I have to pull my pants down. Like an inch- 2inches down past my hip bones. If you know where they typically do C-sections now it's like 1-2 inches under my scar from my C-section. He told me my whole pregnancy with my son that my son was low. But he always found my son's heart rate like 2 inches under my belly button. I read something the other day about a mom having twins and they only found 1 baby HR at first and it was low like it is for me this pregnancy. So now I'm scared I'm having twins.

Twins run every 3-4 generations in my family. I'm the 3rd generation and no twins for my generation yet.

Moms of multiples did they find one of your baby's heartbeat super low in your pelvis?

My Dr does a quick scan at like 9weeks. Barely enough to see there's something in the sac and then he turns off the machine(portable ultrasound machine) so I feel like multiples could have been missed easily.. anatomy scan tomorrow!

White dot is where baby's heart beat is found..