Not as far along as I thought!

So I thought I was 8 weeks preg. Had a period 8/16, then had a weird short period 9/10. Had a couple episodes of possible implantation bleeding, happened 2 different occasions after I wiped. Thought it was weird so I took a test9/22–Positive! I figured my date was 8/16...went to the drs on Wednesday and my ultrasound confirmed exactly 4wks 3days which correlates perfectly with 9/10 as my last period. Anyone ever test that soon and have a positive?!? Def threw me for a loop!!!!! 💙💕💙💕 prayers for a healthy little baby! I go back in 2 weeks for another Ultrasound!