Ok, ladies, I caved and I peed. On the stick. I have no willpower!!
So I used a FRER test and the result is...inconclusive 
When I was watching it develop (as you do) I spotted straight away that the magical second line seemed to be appearing. Then of course the control line developed a nice, strong, obvious purple/pink colour and the second line didn't really get a lot darker. So now I have a test which has one very obvious line and one very faint lilac/greyish line.
Now I know that both lines should be readily visible to the naked eye. And I know that any line that appears after the 5 minute mark is prob an evap line. But I waited the exact 3 mins FRER suggest and then I showed it to DH who is much more of a sceptic and quite clear headed about these kind of things and he said he could see that there was a second line there as well.
I put it down for literally a minute or two and tucked DS into bed and I've just looked at it again and the second line hasn't gotten any darker but it's still...there..just barely..
Anyway, I'm getting very over excited def not going to say this is our first BFP because I'd be wanting that line to be a lot darker and for AF to def not be appearing next week before I break out the Shloer but maybe it's our first May not-BFN??? Maybe??
Going to grit teeth and wait until my designated 9th May testing date to test again tho, if I'm pg I'll still be pg on 9th May and don't want to spend a fortune on hpts with faint, possible lines on them!