hey sounds very similar to me. how old are you? i had one last september very very very heavy like you and havent had another proper one since and before that had had one for ages. i posted a comment and havent had any replies. if you find out what it is please could you let me know?! its stressful

The red clumps looking like tissue is just that. It is the uterus lining being discharged. Some women get it in clumps, some does not

I don't know if this is still of use to anyone, but I had this happen to me about 5 years ago. I was 20 and had never had regular periods. I didn't start my period until I was 16 and then I maybe had 5 or so periods until I was 20. When I was 20 I started having periods every couple of months and then every month and then every couple of weeks until eventually my bleeding didn't stop. My menstral period went from non-existant to constant. It was annoying, but I didn't get concerned until I passed a golfball size red clump. That started my trip to the doctors. I had ultrasounds done and eventually the doctor put me on 3 high dosage birth control pills a day (I was taking a months supply in one week) to stop the bleeding since I would be returning home from college over Christmas break. It took almost 2 weeks for the bleeding to stop and the bleeding stopped for about a week until it came back and was worse. It got to the point that I was a pasty white color and anemic. When I got back to college my dr scheduled an appt immediately and I had an immediate D&C. Basically since I had went so long without having a menstrual cycle, the wall of my uterus kept increasing in size due to all this built up blood that was not being released. Eventually, when I did have a menstrual period, in an effort to bring my uterus back to normal, my body kept shedding that lining of blood until it eventually became a real risk to me.

Be careful with this and get to a doctor, it could be a serious health risk for you.

strangely my period just reappeared last month properly and this month ive had a little one so perhaps its sorting itself out but my mum says if it doesnt soon we'll go to the doctor.
thanks for the info really useful to know thanks