dates don't add up opinions wanted

lovely • Currently a PTA 👩🏾‍🎓future Physical therapist 🎀💍

I have irregular periods at times I’m baffled. My period was December 8th i bled for seven days . So on January 3 I spotted brown discharge for 2 days !! I took a pregnancy test sometime last week & I got bfp :))) I went to my doctors office & got a hcg blood test done on February 21 & the nurse said I was 3-4 weeks I have to be furthef along