Heavy implantation bleeding!!

Brandi
So I'm so shocked!! I had what I thought was my period Dec 13th which was 5 days earlier than when it was due. I usually have 6 days of heavy bleeding and 7th day light. This time around the 1st day was really light, the second was pretty heavy and had to wear a pad, the 3rd was almost nothing. I just assumed my cycle was changing. My boobs started to get more sore as days past. Then this morning hubby and I "bd" me thinking I'm starting my fertile weak (not). After we finished I went to use the bathroom and when I wiped I noticed light pink spotting and two really small brown clots in the toilet (freaked me out). So immediately I took a hpt and it came up dark positive instantly... I'm in total shock because what I thought was my period was indeed implantation bleeding. Has anyone else gone through this and mistaken implantation for af?