Need some heads up

Hi Mummies, I just went for my first checkup at kkh today. According to the scan, i am at 7 weeks but according to the Dr my first day of last period was about 8 weeks ago so it’s not that accurate. Hence she is asking me to come back in about 3 more weeks to do another scan. I just want to know if this is normal? Is there anything that i need to take note of? I’m a first time mum and quite worried. Another thing is, is there a way that i could claim my chekcup bills etc via Medisave? When i’m at the hospital earlier on, nobody went through the payment options with me. But i have seen people were being attended at the “Payment Via Medisave” counter. And i ended up paying cash just now.. Anyone can advice any further?