Honey, I am keeping everything possible crossed for you - I hope you get a scan today and that they find the reason for the bleeding. I have no idea of course, but would find it weird if the HCG is rising as it should, but that the rest is not OK...
I am so sorry you are having to go through this!
One thing I would say ... I think our bodies respond to things differently, like with symptoms, or lack thereof - just because in the past you have responded sensitively, does not mean that you are going to this time... I have had no symptoms whatsoever so far (excepting the mild OHSS and frequent peeing and waking up punctually some time between 3 + 4:15 every morning) - no seriously aching boobs, nothing I would call cramping, no spotting... not even hit that wall of exhaustion yet in the early evenings... Please try to keep calm and I really hope that there will be good news for you today.
As far as a remedy for the low HCG thing - you get healthy pregnancies, where the values just start lower, but rise as they should... then you get others (like Mo - I think hers were pretty high - she was at over 691 at 11dpt - and 2540 two days after that, where I was at 118 yesterday at 9dpt - even if I were to triple in 48 hours, I wouldn't get her numbers
) - my doubling time is 33,84 hours and hers is 38,34 ... your figures are 72 hours - so that does seem slow, but I believe is still within the range that is OK (Mo can say more on that)....
Unfortunately, as painful as it is - none of it is in our hands. We can do our stimming, we can look after ourselves - but as soon as the "artificial" process begins, it is out of our hands. After transfer, we just have to pray that *this time* it works. It is part of the worst thing in this process - being utterly helpless and not able to influence anything