Normal?

So I recently found out I was pregnant. I called my doctor to make my first appointment and they said what they do is make an appointment around 6-7 weeks for a blood test to confirm and make sure I have my prenatals. Why do I have to wait until I’m 7 weeks for a blood test??? Thankfully I started taking prenatal that I bought otc. Is this how it’s normally done?? I thought u get your first ultrasound at 8 weeks?? I don’t know why this is bothering me so much