How long did it take to get a positive pregnancy test after your missed period? Need your opinions... :)?

So I had an "oops" about 2 days before ovulating, and my period, which I've had 3 times since my last baby (who's now 14 months) has been like clockwork, and now I've missed it by 2 days, but I've taken two negative pregnancy tests. I've also had lack of sleep for the last week - maybe not pregnant and this is affecting it...? What do you gals think?