I would be inclined to. My thoughts would be that with an expired test you would be more likely to get a negative result when you are in fact pregnant. The test losing sensitivity rather than giving a false positive. Of course I could be wrong and the opposite is true. :-)
On the other hand just having had used and read the instructions for it sounds like test worked perfectly. Nothing shows up on the screen until you pee on it then you get the hour glass till it comes up pregnant / not pregnant.
You better update :-) and congrats most likely.