Expired pregnancy tests??!!

Tiffany

This may sound like a really stupid question but I'm going to ask it anyway. How accurate are expired pregnancy tests? My cousin got one of those big lots of pregnancy tests on amazon and doesn't need them anymore so she gave what was left to me. After using one this morning and getting a negative result I notice the package said exp 1/17. So it expired about 6 months ago. Can they give false negatives or not read correctly? We are trying and having issues. My period is fairly regular and I am currently 3 days late with no signs of af coming. I'm wondering if I should just trash the tests (so much for trying to save a little $) and buy new ones