6 dpo implantation bleeding?

Please I need help! I’ve seen lots of different post and I’m confused, I’m worried, and curious. Please respond or post your different stories. I’m a mother of 3 and haven’t really been trying to conceive, but haven’t avoided it either, I do however keep track of my cycle with this app. Well this app says I ovulated on December 10th or 11th. Well on December 16th (6dpo)I started spotting it was just normal spotting until December 18 when it got heavier but still lighter than my normal period Which wasn’t due until another week.... I just stop bleeding yesterday December 20th with a little spotting this morning. My period isn’t due until another 2days and I got a bfn a hour ago.Did my period just come early, Or did I just experience implantation bleeding and it’s to early to detect hcg? Please help I have some health concerns which will put me at high risk if I am pregnant and would like to have a jump on care. Somebody anybody help I know all implantation bleeding can be different based on the woman so I know in some cases implantation can last longer then 3days and be as heavy as a normal period.