It is still too early for even the most sensitive blood test...if af is supposed to come on the 22 and today is the 16th that means that you ov'd about 8 days ago...so the implantation stage wouldn't have had enough time to start raising your hormone levels...Wait until the day you are supposed to get af...if nothing then test...sometimes even on the first day of a missed period, a hpt cannot detect the hormone changes...Only time will tell and I think you just have to wait a little longer to get accurate results...are you ttc? PMS symptoms mimic pregnancy symptoms...
try to go for equate at walmart, they are only 3.97 for one and 8.97 for 3. i recommend that because i found a website (sorry cant remember what it was though) clearblue measures from hcg levels from 40 and up. equate can measure from 20 and up (More sensative) i thought the more expensive was better but you never know waht those statistics are based on. good luck!
It is too early especially if you are using a regular (rather than early-result) test.
Check out www.peeonastick.com... this site answers any question you could possibly have about HPTs!!
Good luck to you!