BHCG levels

We are from India. My wifes Bhcg levels are as follows:
LMP – 10.09.2008
IUI done on 25.09.2008 / 26.09.2008
Days since LMP / Days since IUI / Bhcg
33 days / 16 days / 26 mIU/ml
35 days / 19 days / 152
40 days / 23 days / 98
41 days / 24 days / 65
46 days / 29 days / 413
52 days / 35 days / 950
60 days / 43 days / 1250
64 days / 57 days / 1850

Repeated ultrsounds have indicated nothing, not even a sac. Transvaginal scans also indicate nothing and hence doc have ruled out normal pregnancy / ectopic pregnancy. Doctor herself is confused and couldn’t come to a conclusion. Anyway now doc has decided against waiting and have advised to undergo D&C in a couple of days time.
Please throw some light as to what might be the reason for such Bhcg levels and whats the possible treatment and consequencies.
My wife underwent Lap some 12 months ago for polycystic ovaries.
Present symptoms – no periods / spotting / bleeding till date. Occasional discharge. Constant breast pain and occasional abdominal pain. For the last 5/6 days constant bottom pain
We are desparate to have a child and please help us. Rgds/Dinesh