Heavier periods?

What are some reasons I might be getting a heavier than normal period? On day 4. Usually almost dried up/only spotting by now (sorry TMI) but I'm still having bright red blood with clots when I wipe. Also have been having horrible cramps. They're usually bad but go away after day 1 or 2. No chance this is a miscarriage because I tested about 100 times up until my period came (and I've already had a miscarriage so I kind of know what that might be like). Thank you!