period dose this happen to anyone else.

So I just started my period and it's super heavy I started it about 2hrs ago just out of no where I sneezed and the floodgates opened and it's a flood. I have changed my pad 4 times in the last 2hrs that's how heavy my period is and I'm having big clots come out is this normal I usually have very small ones if any at all so I'm not sure if I would be worried or if it's okay. Thanks