TMI - Period Bleeding

Hi, I started my period on Monday and I’ve had very heavy bleeding. I m now 4 days in and it doesn’t seem to be getting lighter. I bleed through my tampon through the night. It seemed to slow down yesterday afternoon but this morning I bled through a regular tampon in 2 1/2 hours, when I changed it I had a clot on there (not big) and when I wiped I saw 2 more small clots. Is this normal? I also had light bleeding two weeks ago and I thought that was my period.. would you go to the ER? I just don’t know if I’m overreacting.