Pregnancy test

My last period was Nov 17th.. (Making it 12 weeks today) 
So, last month I took 6 tests, all first thing in the morning, all negative. Last one being on the 17th. 
I told myself I was going to wait till my birthday (Saturday February 6th) to take another.. Well it was positive! And the next day positive again! So Monday I made an appointment to get a test done at the doctors.. They said since I had to many negatives the month before, that instead they were going to do a blood test. 
My question is: if the pee tests comes back positive why bother with a blood test? 
And is it possible I got pregnant in December or January and just missed December period? So I wasn't as far along in January? Or maybe they were all bad tests.. 
Idk it just seemed weird that they wouldn't try with an easy peesy pee test first. 
Or even and ultra sound? 
So long story short I'm waiting 3-4 days to find out what I already know! :/ annoying. Then ah going to wait a month or so for an ultrasound (why so long cause they are backed up that far) I was able to squeeze in a blood test today, it took 5 minutes..