Confused

Ni

So im currently 6 weeks pregnant and not sure what’s happening. 2 days ago i started spotting brown. Yesterday it turned pink then dark red. Today its dark red and the cramping is intense. I went to my doctor yesterday and he told me oh its implantation bleeding. Its fine. I dont understand how its implantation and the pain and blood is no joke. Im almost sure im going to miscarry. Has anyone experienced this?