Double period in a month?

Hey guys 21f here I started my period last Sunday and it finished later that Thursday. My period was extremely painful and in my last post I posted a picture of a huge clot. Anyways I was at work last night and I thought I was having some heavy discharge but to my surprise I was bleeding extremely heavily. I had stomach pain for the past 3 days and I was having bad back pain. I’ve never had a period twice in a month and especially not a week later. My pregnancy test is negative as well