Hi Kalidasa
Very sorry to hear what you are going through. I had a MC in Dec at 4w 4d, and hope that my experience will be of some use to you during this difficult time as there are so many similarities with your situation.
Like you, I was very aware of my cycle and became pregnant quite quickly after treatment for a condition which can cause infertility. I had symptoms from very early on (strange stabbing pains, nausea and just feeling generally feeling 'odd') and so by the time I got a BFP on 14dpo I had already had an inkling for over a week that I was pregnant.
I was a bit stressed about the pains I was getting but wasn't unduly worried about miscarrying. Then about 4 days later while I was at work, I had a sudden feeling of foreboding, combined with a conviction that I was no longer pregnant. This was followed soon after by a single sharp pain 'down below' and the bleeding started.
To cut what could be a very long story a bit shorter, the bleeding lasted for a week, and I spent the first 2/3 days of that at home mostly in bed. It was kind of like a period, but hard to cope with psychologically as I was so utterly heartbroken when things started to go wrong. Now for the TMI bit - was hard to tell if it was significantly heavier than normal as don't normally use pads, but it was reasonably manageable (compared to the experiences of others I have read about), although lots of clotting and didn't want to stray far from bedroom/loo for those first few days.
Aside from feeling very sad and upset, I was also utterly wiped out and spent a lot of time asleep. I returned to work around day 4 (waited until I had gone 24 hours without bursting into tears) but had to leave early a few times in order to come home and sleep for rest of they day!
I did another test a couple of days after the bleeding had stopped as although I knew it was all over, I started to get returning pregnancy symptoms, which was really confusing. It was negative, and I think that helped draw a line underneath things a bit.
As we all know, bleeding doesn't necessarily mean things have gone totally wrong, and, as Bonzo said, testing won't necessarily tell you what's going on. I tried to accept early on that there was no hope (unlike you, the bleeding was constant, and kicked in with a vengeance after a few hours), but I have heard of a lot of women for whom things have worked out fine, so I will keep my fingers crossed for you.
A few weeks on, things settled down a lot and all the pregnancy symptoms/hormonal madness has faded, although it did take a little while (possibly because my hormones were a bit all over the shop anyway thanks to medical condition). Period returned as normal a couple of weeks later, and ovulation signs kicked in too at expected time.
I really hope you aren't left in limbo for too long - it is such a desperately stressful time, especially when you don't have clear answers about what is happening. Take care, and please let me know if I can be of any more help.