hiya i know how you feel i have spent a fortune on tests, and im wondering weather to get another one as im 9 days late and its doing my head in. I have read so many different comments about the tests saying that people tried for days and days then had a positive one. i have used the clear blue ones and the rubbish ones and still nothing.
Sometimes it takes a couple weeks for a possitive to show. If it was me I would wait a week and take another test, if it's still negative I would go get a blood test from my doctor. I was 3 weeks late once and it was due to a cyst that was hemoraging. My doctor was able to do an ultrasound to see what was going on. I have a history of cysts though, so maybe that isn't it for you. But wait a bit and retest.
Good luck to you two.