Period but got bfp 11 days later...thoughts!?!

Ok so I thought I could be patient but I'm wide awake worrying. We've been trying to convince #2. I had my last period on 9/1 then tracked ovulation with opk and ovulated late. Started what I assumed was a period on 9/25 (pretty normal for me -25 day cycle). It was very heavy, lots of chunks (sorry tmi, not normal for me) and lasted my normal 5 days but then spotted brown mucus for an additional 4 days (which is not normal for me but figured it was because it was so heavy). Took opk on 10/3 and 10/4 both very positive. On 10/5 I felt very nauseous and something told me try a pregnancy test instead of opk and it came back very dark positive right away. I called my doctor and am having a blood test tomorrow 10/6 and will repeat on 10/9.

Has this happened to anyone and what was the outcome????

Thanks in advance for responding!