Usually with pregnancy from what i understand, you will have about a week or two while the egg implants where teh sugars will rise. And then they will drop.
Or your are getting sick.. Or you are stressed.
I would do a PG test to rule it out <or to discover something wonderful!>
I know what you mean about disappointment though <see my siggy...>

And i wish you all the luck in the world with all my fingers crossed for you!!!!!