Help!!

Please help! I normally get my period for around 6ish days. Well, I was extremely tired all this past week (which I've been working more) and then I started Friday night. I was extremely emotional as soon as I started. It hit me like a train. Anyway, Saturday comes and normally I am very heavy (we're talking going through super tampons in 2 hours or less) and all day Saturday I wore regulars and changed every 4-5 hours. Same thing for today (Sunday). Well at 6 o clock today I changed and went back a few minutes ago to change again (around 10pm) and there's nothing there!! My period began late Friday night and is now over on Sunday! What could this mean??? Could it be implantation bleeding?? Do I need to be concerned?? Please help. Thank you.