Two day period?

So on the 15th i got a faint positive pregnancy test and then the next day i got the same thing but started bleeding... and now today the 18th I’ve completely stopped bleeding? It was bright red no clots or anything and it was a medium flow. My periods are normally 7days long so I’m confused. And i used a cheap test today and it says negative. What could this mean? I’ve heard of implantation bleeding but i know it’s not suppose to be bright red and not much blood at all.