Implantation or period? Help!

I am so confused...at first i thought maybe this is implantation bleeding cause it started off brown with light pink blood for a whole day but then I woke up in the middle of the night with horrible cramps and when I went to the bathroom a bunch of blood came out and I had a medium flow all day long so I thought ok I just started my period early but it’s day 3 and my bleeding is completely gone? Has anyone experienced this before?