NEED advice?! 😫🤢

Ok so, 9 months ago I had Bub and the next day I got the implanon inserted. For a month or so I've felt EXTREMELY pregnant but got negative tests. My period was over a week late now all of a sudden I'm bleeding EXTREMELY heavy and I usually have light periods. I'm in so much pain and still bleeding like crazy on day 4. Could this be a miscarriage? I just don't know what else it could be. :(