i went through IUI with pregnyl boosters, and had the last one on the Thursday, tested BFN on Sunday (so four days) and then BFP Monday. i would say hold onto cautious hope at the moment, test again tomorrow - if the line is still there, then it's a great sign, if it's not, it may mean you were just getting an after result form the pregnyl - it really is one of those situations where you need to check again - everyone metabolises pregnyl at a different rate, and most clinics won't accept HPT BFP until 7 days after last booster

hoping it was a true positive and you have just received a fantastic Christmas present

BG