I think the doctor at the end had a point about it being important for infertile people knowing whether they can actually conceive or not. Although the tests themselves must be 100% accurate first.
Normal pregnancy tests give you a strong positive immediately (I tested at 5 weeks and got an immediate answer twice now). I have also spent a fortune on negative tests as I was ttc for 4 years before this pregnancy and have incredibly irregular periods.
As for having pregnancy symptoms and then a heavy period, you may not necessarily be pregnant. Just 2 months before becoming pregnant this summer I had very strong pregnancy symptoms (sore breasts etc and felt awful and "full") and despite a normalish period I did a test - negative. And within days had a terribly heavy period. I bled for 3 weeks in total. The doctor told me that even if I was having a miscarriage the pg test would have still been positive and she referred me for a scan and I had a large ovarian cyst. The following menstrual cycle it had gone (thank goodness) and that was the month I conceived.
So despite suffering very badly and worrying about the cyst, it kick started my reproductive system and I managed to conceive.
It is very important that I know when I am pregnant as soon as possible as I am diabetic and must work extremely hard throughout pregnancy. It isn't just a case of letting nature take its course as I would have a deformed baby if a live one at all. There are other people who must be vigilant through pregnancy too, epileptics and asthmatics etc, so early knowledge is vital.
Thank god we aren't all left to get on with it like our mothers' were.