help...?

I am 2 weeks late as of tomorrow for AF. AF was due 1/7. I Ovulated on 12/25 about 90% sure of it. I have not been late in over a year and a half. and never this late. I did stop my Clomid 2 months ago but my cycles after that were normal. I am still testing negative on all brands of hpt. I am waiting on our insurance cards to come ( the gor lost in the mail, of course) so I can get a blood test... I really want this... it's been 6 years of TTC. But it's hard for me to be hopeful, instead I'm just worried. so any insight or experience would be amazing. I guess im just woundering... has anyone ever been pregnant and not shown up on HPTs for a long time after conceiving????