Is it possible to know that your pregnant 2 weeks and 1 day?

I took a pregnancy test today and it came out positive. I calculated my due date from the first day of my last period and it turns out I'm 2 weeks and 1 day. I didn't know it was possible to know that your pregnant that early I thought it was too soon to tell but maybe I'm wrong I don't know. Is it possible that the test is wrong or maybe I calculated wrong or what's going on I don't know