What Causes Heavy Periods And Sharp Pain?

I have been on my period since last Tuesday, but it s been really heavy for the past 3 days to where I m bleeding through my clothes and having to change my tampon every two hours. Lots of blood clotting also and sharp pains! I don t know whether it something I should take to an ER. I ve been on the implanon birth control also and haven t had a period in a while so I don t know if that s the reason it s causing it or what.