First ultrasound timeframe?

I am now 4 weeks 2 days. I have had several very clear positive tests. I talked to my doctor about making an appt. They said there is no way to confirm and they don’t want to do an appt until 8 weeks minimum. On here I see people with ultrasounds at 5,6, and 7 weeks. Is it odd that my OB is asking me to wait to even come in? This is my first baby so I am new to this and not knowing anything is hard. I will be honest I know the basics but i don’t know everything to do. It makes me nervous to wait.