OMG I can't imagine what you're going through. But when you think about it, w/ each passing hour, it will only get more and more stressful for you, and you are either pregnant or not. I think you will be equally disappointed w/ BFN as w/ coming of AF but at least the stress, the hope will be over. One way or the other you will know...and you MAY BE PREGNANT, and instead of stressing out you could be celebrating!!!
It's up to you, I know it's tough, I waited almost 4-5 days when AF was late w/ my first son, but I wasn't stressed about it, as I was very busy w/ work and friends, and by the time I realized AF was late it was almost 3 days late.
Good luck w/ whatever decision you make, we are all here for you, but if you choose to wait, you have to find a way to relax b/c if you're not preggo, it will delay AF, and if you are, stress is not good for the little one. (If you're preggo you will be very happy no matter what, I just think that if you're not preggo, the longer you wait, the more disappointed you will be.)