Hi there. Sorry for your loss, and that you are having to go through this a second time.
I had a mc recently at 10 weeks, and did have very bad bleeding and need an ambulance / A&E / emergency ERPC. I think I was lucky not to need a transfusion (poor you), they were definitely talking about the possibility at one point, but did go through 5 litres of fluid on 2 drips before I had the surgery. I was told that though my uterus had emptied, "matter" was stuck in my cervix, which couldn't push it out, and that was what caused so much bleeding. The very gushy bleeding did start very suddenly - I had enough time to get to the toilet, that was all, and the cramping didn't start till after the first big gush. Obviously I was a little further on than you are now, but not as far as your first mc, so not really sure how this would compare. I was however told that my pregnancy was only the size of a 5.5 week baby. What I have found on here is that there seems to be a lot of variation between how much bleeding different people have, even at the same stage of pregnancy, and what help they need with the mc, so it's difficult to say something helpful.
If it was not an important time at work, I would say without question that you should phone in sick. You really can't be expected to work at this time. Having said that, I do understand the pressure you must be under with work. How important is today for your job - are you absolutely irreplaceable? How well do you get on with your boss? Does your boss know about the previous miscarriage? Could you phone and explain what is happening, and that last time you got dangerously ill? Can you get home quickly from work if you feel worse?
I don't feel that I've helped much, but didn't want to leave you unanswered, and I guess you will have decided whether to go to work by now anyway.
I hope things will be physically easier for you this time, and that you won't have a repeat of what happened last year. Do take care of yourself, and come back to talk if it would help. x