Implantation Bleeding??

Here’s the thing...I’ve had pretty bad cramps all day, so I really thought I started my period when I first saw the blood this morning. I haven’t bleed a whole lot, and it’s been this color all day. I’m so confused!!! I thought maybe I was pregnant up until this morning, but now I’m confused again! My blood is usually so dark and heavy that it looks almost black. Whats going on!? I’ve taken like 3 tests in the last few days and they all said negative. Sore nipples for over 10 days!?