do pregnancy tests ever "go bad"

[Catbutt Diapers]

I had a few internet cheapies tests left over from TTC Lulu (so they have been sitting in the drawer for nearly 2 years now). I've tested 3 times and all of them have been stark negative - BUT I'm a week late, eating EVERYTHING in sight, and have had sudden on-set evening nausea that goes away just as fast as it comes...