Right.
I know the rules. Disregard tests after the 10 minute window.
However....
On Monday I had my day 21 bloodtests, (and handed in my DH's sample, I cannot explain how weird I felt walking through the hospital thinking "I have sperm in my handbag!") 
Yesterday morning it occured to me that my cycle is ticking on and I have some of the internet cheapies that I bought last month in the bathroom cabinet, and that there is the slimest of chances that I pregnancy might show up. So I POAS with FMU but after a few minutes it was obviously going to be negative so I threw it in the bin. I did the same thing this morning but as I am so impatient I waited only seconds before putting it on the window sill and getting ready for work.
This afternoon I got home from work and glanced over at it. I picked it up and there was the faintest of faint lines.
Now, I have peed on alot of these sticks and I have never had a tide mark before, in my experience pink dye does not do that in the same way the blue ones do. Of course, being insane and a bit grim, I found yesterdays in the bin and compared the two. Today's is definately not my imagination, it's there, but very very light.
So, I would be really grateful for your thoughts, I know I sound desperate but we've been trying for 2 years so I am desperate.
I suppose I'm one of those people who will only truly be happy when Mumsnet invents a test that you can use by pressing a button on the key pad!!!!!