7 day period

My period is always 3-4 days long. Anyways, I had brown spotting for 4 days, it fluctuated between light and heavy. On days 5-7 I had heavy red period. Non stop heavy. With cramps worse than I've ever had them. Then it just abruptly stopped, it didn't get lighter towards the end or anything. I'm also still cramping..(this never happens)
What can this be?