Early Positive? Help!

Hello I need a little help understanding.  I got a positive ovulation test on December 9.  But I think I might’ve actually ovulated on the 8th maybe. Period due December 24th.  I got a positive pregnancy test on December 17th. I am absolutely certain I did not conceive before this cycle.  How did I get a positive so early? My periods are like clockwork and I missed my period on the 24th obviously because I am pregnant. But all the videos I watch and apps say I wouldn’t be able to get a positive that early as the egg would not have even implanted yet?! And would implant in week four? I am so confused as to what is going on. Please help me understand why I got such an early positive. I know for a fact I am not further along than I think. If you have ANY more questions that would help you give advice or suggestions just let me know. 

Dec 9: Ovulated (negative ovu. on 10th)

Dec 17: Positive test

Dec 24: Expected period (missed)