Sorry to read about everyone's experiences.
I've had four, at 7, 10 and two at 11.5 weeks. All different.
Excessive bleeding - if it's lots, liquid and if you feel dizzy, do talk to / go to hospital. It is possible to lose your own blood. When the placenta detaches, it can tear a wound.
I had that with MC2 and ended up in hospital for three days with a lot of IV fluid and a couple of units of blood. Came home with industrial strength iron tablets to get from 'lowest threshold of acceptable iron levels' to normal.
That was a very different experience from the others. Very liquid, whooshy blood, lots of it, rapidly, getting through bath towels. In retrospect it is a little scary that, after the first evening of rapid blood loss, I crawled into bed - literally, as was dizzy - and went to sleep. Woke up in the morning, thankfully. Eased up a bit next morning, worse in the afternoon, went to A+E in the evening, after I was too dizzy to go downstairs, waited until after initial assessment (lying down) before fainting in A+E loo. Was ok lying down, couldn't stand up again until after about 12 hours of IV fluid boosted my BP.
The others were a bit more like massive, three-months worth, periods. First one was a MMC at 10 weeks (hadn't developed beyond about 3). About three days of very heavy period, pain, lots of blood - but more clotty, not whooshy. It did make me think that maybe that's the sort of experience people who have terrible periods experience, painwise. Didn't experience contractions. I got away with paracetamol and cheap champagne (might as well use a painkiller that cheers you up).