HCG/ Blood drawn why?

Octavia
I see so many post about getting blood drawn and HCG levels and doing it every couple of days; kind of freaks me out because I went to my doctor and the only blood work they did was a pregnancy test. Next appointment apparently is for paperwork around 7-8WKs and they said nothing important really happens or starts until around 12WKs is most important..... first baby also I'm currently at 4wks +2