Hi again Naomi,
Quantatative Hcg or QHCG is putting a figure on the level of hcg so it could be 7ml/u and that would say you were pregnant but only just. Usually a woman measures a level of about 50ml/u HCG around when she is due for AF. Qhcg will always give a measurement on the lab report so your doctor will be able to see what the levels were and show it to you. For example if you had a Qhcg of 4 it is possible that you had conceived and things didn't progress. This is commonly termed a chemical pregnancy. I don't like that term to me it sounds really cold. Basically it has been so named as the only way you would know you were pregnant is chemically - meaning through testing.

SeHcg or SHCG or BHCG are basically yes no answers. Yes it's positve or no it's negative. Most labs have a cut off of 5ml/u of hcg for pregnancy. So any lower and you are negative. Does that make sense?
So, from what I have read you have said I am understanding you did a hpt that was positive had a Qhcg that was also negative and then another hpt that was neg and then just a straight Se hcg.
I would feel really comfy in saying that it may have just been a bodgy test and that you should feel secure in the knowledge that you bhcg was negative.
Don't use that brand again! I won't touch them with a barge pole now. I can remember feeling devastated at the false results I got (I wrote about it in BB in December last year).
It is awful and I truly understand what you are going through. I hope this has helped.