EXTREMELY heavy period?

Okay, this may be a bit TMI but I really need help. I'm 13 and I woke up on Friday and found out I'd got my period again but it was quite light. I was glad because my periods are quite heavy usually. However I only came off my period on the 21st of may so this period was quite early. Anyways, today for some reason it came on REALLY heavy. I'm not joking. I soaked through a maxi pad, pyjama bottoms AND bedsheets and I'd only had the pad on for an hour. I've went through 3 pairs of underwear and 4 pads since I woke up and it's only 12:20 PM. I'm also having really bad cramps. I'm just really sick cause I can just feel it coming out ALL of the time and when I stand up I gush so I'm pretty much stuck in my room all day. What is wrong??