In need of advice please

I am currently 22 weeks and 4 days. For my 20 week gender scan, my dr sent me to a prenatal center. So after that one I had to go back last week to the prenatal center again to get better pictures of her blood flow in her heart, they couldn't see good enough the first time. Well my dr called me and told me that he is gonna start me doing my weekly visits at 32 weeks. But didn't say why. Well on Monday when I went for my other scan the dr at the prenatal center told me that she was gonna be the one doing my weekly visits there and I start them in July and I have to have a ultrasound every week until the baby is here. She said that bc I was over weight before I got pregn that I have a really high risk of having a still born baby. N I HAVE TO bc monitored weekly. Well I didn't think I was that big. I'm 5*9 and before I got pregn I weighted 237 and now at 22 weeks I weight 246. And I am just so confused bc I have never heard that before.