Due Date

So I just found out about a week ago that I'm pregnant. My first test was really pale, but I've since taken a couple more and done a urine test at the hospital so I'm definitely pregnant. I took an earlier test around January 17th and it was negative, but I was thinking maybe the conception happened on January 3rd. Would a pregnancy test show up negative that far along? I have also been on birth control for the past couple/few years and just stopped taking it around the beginning of november. I had my first period after that on December 11th. So I think my cycle was kind of weird. My predicted due date is September 22nd (it's saying I'm 8 weeks along). Is that likely? I just want to know how far along I am!! 😊