Don't the pregnancy hormones stay in your system for a while anyway, so you'd still get positive tests even if the worst had happened? And at a certain point don't the hormone levels get so high that tests don't work properly anyway?
I did find the early scan reassuring for a bit and feel more positive having seen a heartbeat but I still can't get those stories about the scans out of my head. Even though I know that most of the people with those stories had probably had the scan because they were already bleeding etc (and I haven't had any).