What Causes Severe Cramps And Heavy Bleeding During Period?

Hello, I'm 20 years old and usually have very regular periods with about average flow and average cramping. However, this month after being two weeks late it came with terrible/almost debilitating cramping and a very unusually heavy and clotty flow (today is day two and i went through a super tampon in 3 hours, a super+ in the next 4 and am using another super currently). And it is somewhat difficult (feels tight) and painful to insert the tampon which is something I've never experienced before. BUT, for the past couple weeks I had been experiencing awful period like cramps (with no period of course), nausea, fatigue, and very much increased appetite which made me concerned about the possibility of a pregnancy, took a test, negative. Is this something to be concerned about or could it just be a bump in my cycle?